HKDSE Physics Electricity and magnetism by topic - HKEAA

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>­ ·C: ·-·- u , ca - 1-1 +-' ca · ·- a, o a u ' .. ■ ■ Ul ·C:- '0 ca .S· ::I C 0 +' a:: ',::( 2 I U- I I ;, I LO ·a, � N C'l Cl Cl) Lil .LU JJ,1 PAST PAPER AL CE DSE BY-TOPIC DSE Physics - Section D : M.C. PD-EMl-M/01 DSE Physics - Section D : M.C. PD-EMl-M/02 EMl : Electrostatics EMl : Electrostatics TI The following list of formulae may be found useful : 3. < HKCE 1984 Paper II - 24 > Coulomb's law + X Electric field strength due to a point charge Two uncharged metal spheres in contact are suspended by dry cotton threads. When a positively charged rod Xis brought near them as shown above, the distnOution of charges on the spheres will be 00 A. B.o:J C. D. Electric field between parallel plates (numerically) Use the following data wherever necessary : 4. < HKCE 1985 Paper Il- 33 > Acceleration due to gravity g = 9.81 m s-2 (close to the Earth) Charge of electron e = 1.6 x 10- 19 C + X Electron rest mass mo = 9.11 x 10- 31 kg Permittivity of free space Two uncharged metal spheres are suspended by insulating threads as shown in the diagram. A plastic sheet is put between them. When a positively charged rod Xis brought near them as shown, which of the following diagrams shows the resulting charge distnbution of the spheres ? nm A B c. Ch vµ � Part A : HKCE examination questions .� .rh Ct---] 1. < HKCE 1981 Paper n- 26 > ti s. < HKCE 1986 Paper II - 28 > Two light conducting spheres are suspended from two silk threads as shown. If they are found to attract one another' which one of the following conclusions is/are correct? (I) They carry smri1ar charges. The diagram shows two conducting spheres X and Y mounted on insulating stands. Sphere X carries positive charges and (2) They carry opposite charges. sphere Y carries negative charges. As Yis moved slowly towards X(but without touclringXJ the total charges onX (3) Only one of them is charged. A. increase and are positive. A. (2)only B. remain unchanged. B. (3) only C. become negative. C. (1) & (3) only D. disappear. D. (2) & (3) only tttttt 6. < BKCE 1987 Paper II- 37 > 2. < BKCE 1982 Paper II - 35 > In the figure shown, an electron travels in a horizontal direction and enters a uniform electric field. The direction ofthe electric field is as shown. What is the direction of the force due to the electric field acting on the electron? A. upwards B. downwards C. into the page D. out ofthepage Three metal spheres X, Y and Z areplaced in contact as shown. A negatively charged rod is brought near z. The sphere yis then earthed while the charged rod is still nearby. 'Which of the following statements is/are true? (1) Xis negativelycharged. 7. < HKCE 1988 Paper II- 28 > (2) Y is neutral. A positively charged metal sphere Xis brought near an uncharged metal sphere Y as (3) Z is positively charged. shown. Y is then touched momentarily with a finger. Xis then taken away. Y is now A. (3) only A. positively charged. B. (I) & (2) only B. negatively charged. C. (2) & (3) only C. negatively charged on the left side and positively charged on the right side. D. (!), (2) & (3) D. positively charged on the left side and negatively charged on the right side. DSE Physics - Section D : M.C. PD-EMl-M/03 DSE Physics - Section D : M.C. PD-EMl-M/04 EMl: Electrostatics EMl : Electrostatics :ti: 8. < HKCE 1990 Paper Il 30 > w 14. < HKCE 1995 Paper Il • 29 > X y A positively-charged metal sphere is mounted on an insulating stand. When the sphere is earthed with a finger, A. protons will move from the sphere to the earth. B. protons will move from the earth to the sphere. C electrons will move from the sphere to the earth. D. electrons will move from the earth to the sphere. 9. < BK.CE 1991 Paper 11 � 29 > Two insulated uncharged metal spheres X and Y are in contact with each other. A positively charged rod is brought nearXas w In the figure shown, X and Y are two insulated metal spheres in contact with each shown above. Which of the following diagrams correctly shows the distribution of charges on the spheres? A. CD other. A negatively charged object C is brought near X Xis touched momentarily B. with a finger, and thenX and Y are separated. The charges onXand Y are SphereX Sphere Y A. positive positive D. CD B. positive C. negative C. negative negative D. positive "'° 10. < HKCE 1992Paper Il 30 > w 15. < HKCE 1996 Paper II - 29 > A positively charged rod is brought near an insulated uncharged metal A small conducting sphere is suspended by an insulated thread. When a positively sphere as shown in the figure. If1he sphere is earthed with a finger, charged rod is brought near the sphere, the sphere is attracted as shown. Which of A. positive charges flow from the earth to the sphere. the following is/are reasonable dednction(s) ? B. electrons flow from the earth to the sphere. (1) The sphere may carry a positive charge. C. electrons flow from the sphere to the earth. D. the sphere is completely discharged. (2) The sphere may carry a negative charge. (3) The sphere.maybe neutral. 11. < HK.CE 1993 Paper Il 31 >w A. (2)only B. (1) & (3) only An uncharged light conducting sphere is suspended by an insulating thread. The metal dome of an operating Van de Graaff C. (2) & (3) only generator is brought near the sphere. Which of the following statements best descnl>es the motion of the sphere ? D. (1), (2) & (3) A. The sphere remains stationazy. B. The sphere moves away from the dome. C. The sphere moves towards the dome, touches it and remains there. 16. <HKCE 1997Paperll- 27 > D. The sphere moves towards the dome, touches it and then moves away. The following are the steps to charge an isolated metal sphere by induction, but they are in the wrong order. (1) Removing the finger away from the metal sphere. 12. < BKCE 1994 Paper n- 25> (2) Touching the metal sphere with a finger. Which of the following involve(s) the application of electrostatics ? (3) Bringing a positively charged rod near the metal sphere. (I) A photocopier (4) Removing the positively charged rod away from the metal sphere. (2) A precipitator in the chimney ofa coal-fired power station (3) A VandeGraaffgenerator Which of the following shows the correct order? A. (3) only A. (2), (3), (4), (1) B. (1) & (2) only B. (3), (2), (1), (4) C. (1) & (3) only C. (3). (2), (4), (1) D. (1), (2) & (3) D. (3), (4), (2), (1) 13. < BKCE 1994 Paper Il- 24 > 17. <HKCE1998Paperil-29> An Ulllulated charged metal rod is brought near an insulated uncharged metal Three insulated uncharged metal spheres X, Y and Z are placed in sphere as shown in the figure. Which of the following can charge the sphere? (I) Touching the sphere momentarily with a finger. W2/Jc__+_+�+�/ contact as shown. A negatively charged rod is brought near X and sphere Y is then earthed momentarily. If the charged rod is still near X y z (2) Touching the sphere momentarily with the rod. X, which ofthe following descnDes the charges onX, Y and Z? (3) Touching the rod momentarily with a finger and then touching the sphere momentarily with the same finger. SphereX Sphere Y SphereZ A. (1) only A. positive zero "" W-0 B. (1) & (2) omy B. positive negative C. (2) & (3) only C. positive positive positive D. (1), (2) & (3) D. "'° ze,o ze,o DSE Physics - Section D : M.C. PD-EMl-M/05 ! DSE Physics - Section D : M.C. PD - EM1 - M / 06 EMl : Electrostatics / EM l Electro stati s lh====:::;:;;��;::::::: ���;:,:::;::;.c;::============aa::.l . 18. < HKCE 2000Paper 11- 28 > 21. < HK.CE 2003Paper II - 31 > + t"'" ' . -----------•' - . '' •' ' ': • C 'l ''' ''' - L --------- >. -l + Four point charges of equal magnitude are placed at the four vertices of a square. The signs of the charges are as shown. A Two insulated uncharged metal spheres X and Y are p laced in contact. A positively-charged rod is brought near X as shown pciint charge C is placed at the centre of the square. What will be the direction of the resultant electrostatic force, if any, above. Xis then earthed momentarily. The charged rod is removed and the two spheres are then separated. Which of the acting on C? following dc:scnbes the charges onXand Y? A. ➔ SphereX SphereY B. t A. negative negative B. negative uncharged C. The resultant force acting on C is zero. C. positive positive D. It cannot be determined sincethe sign of C is not given. D. uncharged uncharged 22. < HKCE2004Paper ll - 27 > 19. <HKCE 2001Paper1I - 28 > Three conducting spheres are suspended by separate nylon threads. When any two of them are brought near each other, they attract each other. Which of the following deductions is correct? A. All three spheres are charged. B. Only one sphere is charged and the other two are uncharged. C. One sphere is uncharged and the other two carry like charges. B D. One sphere is uncharged andthe other two carry ualike charges. A Two charged spheres _A and B hanging at a point on a ceiling by two identical nylon threads. They remain at rest as shown above. Which of the following statements must be correct? 23. < HK.CE 2005 Paper II - 17 > (1) Both spheres carry positive charges. Two conducting spheres are hanging freely, in air by insulating threads. In which of the following will the two spheres attract (2) The force acting on B byA is larger thanthe force acting onA by B. each other? Note: 'N' denotes that the sphere is uncharged. (3) The mass ofA is largerthanB. (!) (2) (3) A. (1) only B. (3) only C. (1) & (2) only D. (2) & (3) only + + N N 20. <HKCE2002Paperll-31> A. (1) on ly B. (2) only C. (3) on ly D. (!), (2) & (3) 24. < HKCE2006 Paper II- 22 > A rubbed plastic ruler can attract paper scraps before actually touching them. Which of the following descriptions about the A plastic ruler is placed close to a stream of running water coming from an insulated tap. The stream of water is attracted charges on the rubbed ruler and the original charges on the paper scraps are possible? towards the ruler as shown above. Which of the follcrwing statements are correct ? (1) The ruler and the paper scraps carry opposite charges. (1) The ruler carries an electric charge. (2) The ruler and the running water are attracting each other with forces of equal magnitude. (2) Both the ruler and the paper scraps are uncharged. (3) Both positive and negative charges are induced on the running water (3) The ruler carries charges and the paper scraps are uncharged. A. (1) & (2) only A. (1) & (2) only B. (1) & (3) only B. (1) & (3) only C. (2) & (3) only C. (2) & (3) only D. (!), (2) & (3) D. (!), (2) & (3) PD-EMl-M/08 1 DSE Physics - Section D : M.C. PD-EMl-M/07 DSE Physics - Section D : M.C. EMl : Electrostatics EMl : Electrostatics 2S. < HKCE 2007 Paper ll - 19 > 29. < HK.AL 1985 Paper I - 45 > t p Q a.,.,:::; highvo::l J -C In the above figures, P, Q, Rand Sare identical light conducting spheres and they are hanging freely by insulating threads of the same length. Which of the following deductions is/are correct? A light conducting ball is placed between two metal plates connected through an �eter to a de. s� e of high volta? e. (1) P and Q must carry like charges. The ball shuttles back and forth between the plates, making alternate contacts with each plate. Which of the followmg statements are correct ? (2) R and S must carry un1ilre charges. (3) P and Q must carry the same amount of net charges. (I) The ball carries charges, sometimes positive, and sometimes negative. A. (1) only (2) Ifthe separation ofthe metal plates increases, the :frequency of oscillation of the ball decreases. B. (2) only (3) The galvanometer shows a current flowing always in the same direction. C. (I)&(3)only D. (2) & (3) only A. (1) & (2) only B. (1) & (3) o,ly C. (2) & (3) only D. (!), (2) & (3) Part B: HKAL examination questions {);HI{AL 1987 Paper I- 30 > □ I , +lC -lC 26. <BKAL1982Paperl-27> The diagram shows a negative charged particle inside a uniform electric field E ' ''' pointing in downward direction. At the instant shown, the particle is tzavelling ''' ' in the direction of the arrow v. Which of the anows 1 to 4 gives the direction of '' ' the acceleration of the particle at this instant? '' '' A. 1 B. 2 '' y C. 3 D. 4 Et +'s Q -lC Three charge + I C, - 1 C and - 1 C are fixed at the comers W, Xand Yrespectively of a square as shown. A fourth charge, Q, is fixed atZ. Ifthe net electrostatic force acting on the charge atXis indicated by the mow, what is the magnitude of Q? 27. < BKAL 1983 Paper I- 20 > A. -.Jzc 2 Two parallel metal plates are placed horizontally with a separation of 0.05 m. A voltage of2000 Vis connected across the B. + ✓ C plates. An oil drop carrying a charge of - 1.6 x 10-19 C is found to be at rest between the plates. Find the mass of the drop. C. -2./zC (Take the acceleration due to gravity to be 10 m s-2.) D. +2$C A 1.6 X 10 -18 kg. B. 1.6 X 10-15 kg. C. 6.4 X 10-14 kg. 1 31. < HKAL 1990 Paper I - 27 > D. 6.4 x 10-16 kg. 28. < BKAL 1983 Paper I - 40 > Which ofthe following statements about the coulomb is/are cornet? (1) When one coulomb of positive charges flows across a potential difference of one volt from higher to lower potential, one joule of electrical energy is given out. A light conducting sphere is hanged from a long insulating thread It is placed between two oppositely charged metal plates (2) The force exerted on a charge of 1 coulomb in an electric field of 1 volt per metre is I newton. connected to a high voltage supply. If the sphere is given a negative charge, it will (3) One coulomb is the total charge of one mole of electrons. A. move to the positive plate and stick to it A. (1) only B. move to the negative plate and stick to it. B. (3) only C. oscillate, touching each plate in tum, beginning with the positive plate. C. (1) & (2) only D. (2) & (3) only D. oscillate, touching each plate in tum, beginning v;ith the negative plate. DSE Physics - Section D : M.C. PD-EMl-M/09 DSE Physics - Section D : M.C. PD-EMl-M/10 EMl : Electrostatics EMl : Electrostatics 32. <BKAL 1993 Paperl-35> 36. <BKAL 2005 PaperllA-13 > [,:!"-' =ml + pl,to r A negatively charged oil drop is kept stationary between two horizontal metal plates connected to a d.c. supply as shown. almninium The oil drop then acquires an additional negative charge. Which of the following changes will be able to hold the oil drop '°""'t � �--�EHT--- stationary? (1) Disconnecting the plates from the supply and moving the plates closer (2) Keeping the separation between the plates unchanged and increasing the p.d. between the plates Two parallel metal plates are connected to the terminal of an EHT. When a charged aluminium foil strip is placed between (3) Keeping the p.d. between plates unchanged and moving the plates further apart. the plates, the deflection of the foil is shown in the above :figure. Which of the following statements is/are correct ? A. (l)only (1) The charge on the foil is negative. B. (3) only (2) Ifthe separation between the two plates decreases, the deflection of the :full increases. C. (1)& (2) o oly (3) When moving the foil towards the positive plate, the deflection ofthe foil increases. D. (2) & (3) ool y A. (l)only m B. (3) only C. (1) & (2) only 37. <BKAL2007PaperIIA-14> D. (2) & (3)ooly 33. <HKAL 2000 Paper IIA- 26 > Two parallel plates are connected to anE.H.T. supply giving a d.c. voltage of 4.5 kV.· If the separation ofthe two plates is set at 1.5 mm, calculate the acceleration ofan electron placed inside the plates. A LOxl09ms-2 +Q 360 B. l.2x lQUm s-z C. 1.6 x 101s m s-z The above :figµre gives the electric field strength (in arbitrary units) at various points near an isolated point charge +Q. D. 5.3 X 1Ql7mg-l 'Which of the following correctly gives the electric field strength (in the same arbitrary units) atX and at Y? electric field strength at X electric field strength at Y 34. <BKAL2003 Paper IIA-23 > A. 72 30 B. 72 36 The magnitudes of the charges on two identical small metal spheres are in the ratio 5 ; 1. The electrostatic force between th.em is F1. If they are brought into contact and then separated to their respective original positions, the electrostatic force c. 90 30 between them becomes F2. Which of the following m.a:y be the magnitude ofthe ratio Ft : A? D. 90 36 (1) 5: 9 (2) 5,4 38. < BKAL 2007 Paper IIA- 13 > (3) s,2 A {1) only O: B. (3) only '¢ C. (1) & (2) only 0: D. (2)& (3) only ' ' y 35. < HKAL 2005 Paper IlA- 12 > X l; Yand z.are small identical metal spheres. X and Y are fixed at a certain separation in air and they carry charges of the The figure shows two small charged spheres X and Y suspended by identical nylon threads from a fixed point 0. At same magmtude. The attractive force between them is F. Sphere Z is initially uncharged. It first touches X and then it equilibrium, the threads OX and Ofmake angles 0 and ¢ ( 0 < ¢)with the vertical. Which ofthe following conclusions must touches Y. What is the electrostatic force betweenXand Y after Z is taken away? be correct? (1) Both X and Y carry positive charges. A. ¼F (2) The charge onX is greater than that on Yin magnitude. B. tF (3) The mass ofXis greater than that of Y. A. (I) only C. ¾F B. (3) only D. 'fF C. (l)and(2)only D. (2) and (3) only PD-EMl-M/11 PD-EMl-M/12 DSE Physics - Section D : M.C. 1 DSE Physics - Section D : M.C. 1 EMl : Electrostatics EMl : Electrostatics 39. < HKAL 2008 Paper IlA-14 > 43. X y +Q -2Q A point charge +Q is fixed at pointXwhile another point charge-2Q is fixed at point Yas shown. Ex andEy denote the magnitude of the electric field due to the point charge atX and Y respectively. For the points on the line passing throughX and Y, how many ofthem haslhave Ex = Ev and how many has/have zero resultant electric field ? (No need to consider the points at infinity.) A small neutral conducting sphere is suspended by an insulated thread. When a positively charged metal rod is brought near A. There are 3 points with Ex = Ev and the resultant field is zero at 2 ofthem. the sphere, which of the following consequences are correct ? B. There are 2 points with Ex =Ev and the resultant field is zero at both of them. (1) The sphere is attracted by the charged rod due to the induced charge on the sphere. C. There are 2 points with Ex =Ey and the resultant field is zero at 1 of them. (2) The sphere is repelled from the charged rod after touching the charged rod D. There is 1 point with Ex= EY and the resultant field is zero at that point. (3) The sphere finally carries positive charge. A. (I) & (2) oc ly 40. < BKAL 2009 Paper llA - 33 > B. (1) & (3) only C. (2) & (3) only A potential difference of 3 kV is applied across two horizontal D. (!), (2) & (3) metal plates of separation 1.5 cm. A charged oil drop ofmass +3 kV negatively 9.6 x 10- 15 kg is kept stationary between the plates as shown. charged oil Find the quantity of charge acquired by the oil drop? d,op 44. (Tal<:e the acceleration due to gravity as 10 m s-2.) A. 1.6 X 10-19 C B. 3.2 X 10-19 C c. 4.s x w--- 19 c D. 6.4 X 10-19 C Part C : Supplemental exercise When a plastic ruler is placed close to pieces of small paper, some of them are found to be attracted towards the ruler. Which of the following statements is/are correct ? '.Yrr 41. Two insulated uncharged � spheres X and Y are placed in contact. X y (I) The attraction is due to the electric force between the ruler and the pieces of paper. A positively-charged rod is brought near X as shown. Xis then earthed momentarily. The charged rod is then removed. Which of the following (2) Those pieces of paper attracted by the ruler remain neutral. descnDes the charges onXand Y? (3) The attraction acting on each piece of paper is greater than the attraction acting on the ruler by that piece ofpaper. SphereX Sphere Y A. (1) only A. negative negative B. (3) only B. negative uncharged C. (1) & (2) only C. positive positive D. (2) & (3) o cly D. uncharged uncharged 4S. 42. (±)-----1----L---!-----G) 2 �- '' ---------:f '' ' ' 3 '' : 4 : ' Two identical spheres carrying equal amount of positive charges are placed as shown in the figure above. Which of the ' '' following statements are correct? t----------i (1) At the mid-p:iint Ybetween the two spheres, it is a neutral point +Q -Q (2) Ifa small negative charge is placed at polntX, it experiences a net electric force towards the left. Point charges, each of magnitude Q, are placed at three corners ofa square as shown in the diagram. What is the direction of (3) If a small positive charge is placed at point Z, it experiences a net electric force towards the right the resultant electric field at the fourth comer? A. (!) & (2) ocly A Directionl B. (!) & (3) only B. Direction2 C. (2) & (3) only C. Direction 3 D. (I). (2) & (3) D. Direction4 DSE Physics - Section D : M.C. PD-EMl-M/13 DSE Physics - Section D : M.C. PD-EMl-M/14 EMl : Electrostatics EMl : Electrostatics 46. ----+----+----+----+---- D so. A B C A, B, C., D � four points on a strai � line as shown in the di agram. A point charge+ Q is fixed at A. When another point _ charge -Q 1S mov:ed fromB to C, which of the following statements is/are correct? • y (1) The electrostatic force between the two charges increases. (2) The magnitude of the electric field strength at the pointD in creases. (3) PointB becomes the neutral point. A. (1) only The above figure shows the electric field pattern around two point charges P and Q. Xis the mid-point between P and Q. Y B. (2) only is a neutral point. Which ofthe following deductions is/are correct 1 C. (1) & (3) only D. (2) & (3) only (1) Both charges P and Qare positive. (2) The magnitude of chargePis greater than that of Q. (3) The electrostatic force acting on Q byPis greater than that onPby Q. 47. The charge on theuraniui:nnucleus is 1.5 x 10-17 Cand the charge on the a.-particle is 3.2 x 10-19 C. What is the electrostatic force between a uranium nucleus and an a-particle separated by 1.0 x 10-13 m? A. (1) only A 4.32 x l0--33 N B. (1) & (2) only C. (2) & (3) only B. 4.32 x 10-2° N D. (1), (2) &(3) C. 43Zx10-13 N D. 4.32N supply. Neglect 51. A charged particle is accelerated across the gap between two parallel plates connected to a constant voltage the effect of gravity, the kinetic energy gained by the particle in crossing the gap depends on 48. What is the magnitude of the electric field strength at a distance r from an isolated stationary nucleus of proton number (1) the mass of the charged particle (atomic number) Z? A z, (2) the separation between the two parallel plates 411:&0r (3) the voltage across the two parallel plates B. (Z e)1 A. (1) only 41ts 0r2 B. (3 ) only C. (1) & (2) only c. Ze D. (2) & (3) only 41ts0 r2 D. Zez 41tc0 r Part D : BKDSE examination questions 49. 52. < HKDSE Sample Paper IA- 24 > Two conducting spheres are hanging freely in air by insulating threads. In which of the following will the two spheres attract each other? Note: 'N' denotes that the sphere is uncharged. (1) • (2) • (3) ' Thediagram. shows a pattern of electric :field lines in whichx; YandZ are points marked on one of the field lines. It would be correct to say that z. (1) the electric field at Xis weaker than that at + + N N z (2) a negative charge placed at Z would experience an electric force to the left along the tangent of the field line at (3) the force exerted on a charge at Ywould be greater than ifthe charge were placed atX A. (1) & (2) owy A. (1) only B. (1) & (3) only B. (2) only C. (2) & (3) only C. (3) only D. (1).(2)&(3) D. (1), (2) & (3 ) DSE Physics - Section D : M.C. PD-EMl-M/15 DSE Physics - Section Ji : M.C. PD-EMl-M/16 1 1 EMl : Electrostatics EMl : Electrostatics 53. < HKDSE Sample Paper IA - 32 > 58. < HKDSE 2013 Paper IA- 24 > The figure shows the location of an isolated charge of size +Q. The magnitude Xand Y are two small identical metal spheres carrying charges -2Q and +6Q respectively. WhenXand Y are separated by a of the electric field strength is marked at certain points. What is the magnitude certain distance, the magnitude ofthe electrostatic force between them is F. of the electric field strength atXand Y? electric field strength atX X X y @--r � electric field strength at Y A. B. c. 72 72 90 30 36 30 72 y \ D. 90 36 40 Toe spheres are �ught to touch each other and then placed back to their original positions. The electrostatic force between +Q 360 them becomes 54. < HKDSE Practice Paper IA- 24 > A ¼ F, attractive B. ¼ F, repulsive X-- y- �---�p:.:.----:----�---�:----� r--- T- ---, --,----T-- -.,- - --,---r---, ---,----, C. ½ F, attractive D. ½ F, repulsive q 59. < HKDSE 2014 Paper IA- 20 > Three identical point charges q (represented by dots) are situated in the space as shown. 'Which of the following descriptions about the direction and Jllagnitude of the electric field£ atXand at Yis correct? Direction Magnitude -A.... Same Ex> Ey --,,__· Same Ex< Ey C. Opposite Ex> By D. Opposite Two insulated uncharged metal spheres X and Y are placed in contact A positively-charged rod is brought near Xas shown. Ex< Ey Xis then touched by a finger momentarily and the two spheres are then separated by removing Y. The charged rod is removed afterwards. Which of the following describes the charges onX and Y? 55. < .HKDSE 2012 Paper IA - 25 > sphereX sphere Y W X Y Z ------------1------ ---@----!----+-- -i----- O··· --- ---- ;------- A. uncharged uncharged +2Q M -Q B. uncharged positive Two point charges +2Q and -Q are situated at fixed positions as shown. Mis the mid-point bet\veen the charges. W, X, Y c. negative uncharged and Z are points marked on the line joining these two charges. At which point could the resultant electric field due to the two D. negative negative charges be zero ? A. w B. X 60. < HKDSE 2014 Paper IA- 22 > c. y Two parallel metal plates P and Qare maintained at a certain p.d. by a battery D. Z (not shown in the figure). An electron placed between the p lates would experience an electrostatic force of 8.0 x 10-18 N towards P. Which of the 7.,"'. 56. < HKDSE 2012 Paper IA- 24 > following descriptions about the electric field E between the plates is correct ? A. E=0.02NC-1 fromQtoP . p� ,:;: P, Q,R, Sare charged objects. When two of them are brought close to each other, P and Q repel, Rand S also repel while B. E=0.02NC-1 fromP toQ QandR attract each other. Which ofthe following descriptions about their charges .is/are correct? C. E=S0NC- 1 fromQtoP (1) P and R are negatively charged. D. E=S0NC-1 fromPtoQ (2) Q ands are positively charged. (3) Pis positively chaiged and Sis negatively charged. A. (l)only 61. <BKDSE2014PaperIA-21> B. (3) only c. (1)& (2) only Q, Q, Q, D. (2) & (3) only Three point charges Qi, Qi and 0 are :fixed on a straight line with 0 at the mid-point of Qi and 0. The resultant 57. < HKDSE 2013 Paper IA- 25 > electrostatic force on each charge is zero. Which oftbe following can be the sign and the magnitude (in the same arbitrary Llghtning flash may occur when the strength of the �lectric field (assumed uniform) between a thundercloud and the ground units) of Q1, Qz andQ3? reaches �C:.1• A lightning flash on average discharges about 20 C of charge. If a thunderdoud is at a height of Q, Q, Q, . ..2 .o:!>_:a;i�ovethe ground, estimate the order ofmagnitude of the energy released in a lightning flash. A. 106 J A. +2 +1 +2 B. 10s J B. +2 -1 +2 C. 1010 J C. -4 +1 +4 D. 1012 J D. -4 +1 -4 DSE Physics - Section D : M.C. PD-EMl-M/17 DSE Physics - Section D : M.C. PD-EMl-M/18 EMl : Electrostatics EMl : Electrostatics 62. < HKDSE 2015 Paper IA- 21 > 66. <HKDSE2017PaperlA-23> Three conducting balls are suspended by insulating threads. Any two of them are found to attract each other ifbrou� close A point charge +Q is fixed at a distanced away from the origin Oas shown. to each other. Which conclusion below is correct ? A. Only one ball is uncharged while the other two carry like charges, +Q 0 ___,,,______;:__________-,.x B. Only one ball is uncharged while the other two carry unlike charges. C. Only one ball is charged. Which of the following graphs best represents the variation of the electric field strength E along the x-axis ? (Take the D. All three balls are charged. electric field pointing to the right as positive.) A. B. E E 63. < HKDSE 2015 Paper IA- 22 > -4Q +Q w X y z 0 X 0 X -d -d Two point charges -4Q and +Q are fixed as shown. At which point indicated in the figw-e is the resultant electric field due to : : these two charges zero ? A. w &. X C. D. C. y D. Z __J_J.:::====+ 64. < BKDSE 2016 Paper IA - 24 > -----+-----➔ +4Q +Q------► x X -d: -d: 0 0 15= 0 Point charges +4Q and +Q are fixed on the x-axis with +4Q at the origin O and +Q at x = 15 cm as shown. The respective electric fields due to the two charges are equal at 67. <HKDSE 2019 Paper IA-23> A. x = lOcm. B. x = 12cm. C. x=20 cm. D. x=30cm. 65. < HKDSE 2017 Paper IA- 22 > In the figure, two charged conducting spheres of the same mass m are put in a vertical plastic cylinder. The inner wall of the cylinder is smooth. The spheres are separated by a distance d and remain in equ.ilibrium. Which of the following statements MUST BE correct? (1) Both spheres caa:ypositive charges. (2) The amount of charges on the two spheres arc the same. (3) The separation d depends on m. A (1) only B. (3) only C. (1) & (2) only D. (2) & (3) only DSE Physics - Section D : MC. Solution PD-EMl-MS/01 DSE Physics - Sectiori1) : MC. Solution PD-EMl-MS/02 EMl : Electrostatics EMl: Electrostatics HKEAA's Marking Scheme is prepared for the markers' refc:rence. It should not be regarded as a set of model answexs. Students and t:eacbel1 who are not involved in the marlcing process are advised to intczpret the Marking Scheme with care. 5. B Sphere Xis not in contact with. other bodies, M.C. Answers thus the total charges on sphere Xmust remain unchanged. I. D 11. D 21. C 31. C 41. A 51. B 61. D 2. C 12. D 22. D 32. C 42. A 52. D 62. B 6. A 3. C 13. B 23. D 33. D 43. D 53. B 63. D Electron carries negative charge, thus the electric force on an electron is opposite to the direction of the EMfield. 4. A 14. C 24. B 34. C 44. C 54. D 64. D Therefore, the electron experiences an upwards electric force inside the parallel plates. 5. B 15. C 25. A 35. B 45. A 55. D 65. B 6. A 16. B 26. D 36. B 46. B 56. B 66. D 7. B 7. B 17. A 27. D 37. B 47. D 57. C Bringing (+) charged sphere X towards Y and then earthing, negative charges are induced on Y. 67. A 8. D 18. A 28. C 38. B 48. C 58. D WhenX is removed, f carries negative charges that would distnbute uniformly on the whole surface. 9. D 19. B 29. D 39. C 49. D 59. C 10. B 20. D 30. D 40. C 50. B 60. D 8. D The(+) charge sphere is earthed M.C. Solution ⇒ the sphere becomes neutral 1. D ⇒ electrons flow from the earth to the sp here(as proton does not move) " (1) Repulsion exists between similar charges. ✓ 9. D (2) Attraction exists between opposite charges. ✓ When the negatively charged object C is brought nearX, (3) Attraction exists between a charged body and an uncharged body. (+) charges are induced on the left side ofX and(-) charges are induced on the right side ofY. 2. C When Xis touched momentarily with a finger, the(-) charges on Yflows to the earth but the(+) charges on Xis still attracted by C. Bringing(-) charge towards Z ⇒ {+) charge induced on 2 and(-) charge induced onX WhenX and Y are separated, X carries (+} charges and Y is neutral. Y is earthed ⇒ (-) charge onXrnoves to the earth but(+) charge on Z is still attracted by the charged rod Finally, X and Y are neutral and Z is positively charged 10. B 3. Bringing(+) charged rod ⇒ (-) charge induced at left.side ofthe sphere and(+) charge at ri�t side of the sphere C Bringing(+) charged rod towards right ball Earthed with a finger ⇒ electrons flow from the Earth to the sphere to neutralize the(+) charge at the right side ⇒ (-) charge induced on right side of the right ball 11. D ⇒ (+) charge induced on the left side of the left ball When the sphere is brought near, attraction e_xist5 between the charged dome and the neutral sphere. 4. A After touching, the sphere shares some like charges and thus repulsion exists to move it away. Bringing (+) charge towards right ball ⇒ (-) charge induced on right side of the right ball 12. D ⇒ (+) charge induced on the left side of the right ball (as plastic sheet does not allow flow of charge) ✓ (1) Photocopier makes use of electrostatic charge to give photocopying ⇒ (-) charge induced on right side of the left ball ✓ (2) Precipitator makes use of electrostatic charge to attract the coal dust ⇒ (+) charge induced on left side oftbe left ball ✓ (3) A Van de Graaff generator gives large amount of electrostatic charge for demonstrating DSE Physics - Section D : M.C. Solution PD-EMl-MS/03 DSE Physics - Section D : M.C. Solution PD-EMl-MS/04 EMl : Electrostatics EMl : Electrostatics 13. B 19. B ✓ (1) Since the two spheres repel, the two spheres may both carry(+) charge or both carry(-) charge (1) Bringing positively charged rod near the sphere ⇒ (-) charge induced at the left side and(+) charge induced at the right side of the sphere (2) Since the force acting on B by A and the force acting on A by B are action and reaction pruI, ⇒ upon earthing, electrons flow to the sphere to neutralize the(+) charge at the right side they must be equal in magnitude but opposite in direction .·. the sphere finally carries negative charges. ✓ (3) Assume the electric force F acting on the sphere is approximately horizontal ✓ Touching the sphere with the rod would make the sphere share some positive charges. Resolving the tension into two components (2) Positive charges of the rod are discharged upon earthing by the finger Tcos0=mg and Tsin0=F tanB=_!_ (3) mg but the human body always remains neutral without carrying net charge mg For sphere A, Bis smaller, tan 0is smaller, thus mis greater. :. no charge is shared with the sphere by the finger, thus the sphere remains neutral 20. D 14. C ✓ (1) Water is neutral, as the ruler attracts the water, the ruler must carry an electric charge. Due to attraction between unlike charges, negative charge is induced at the left side ofX ✓ (2) The attractive forces between the running water and the ruler are action and reaction pruI, Due to repulsion between like charges, positive charge is induced at the right side ofY. so they are of equal magnitude. ✓ (3) The side of the running water near the ruler would induce the opposite type of electric charge 15. C while the side of the rw:ming water further away from the water would induce the same type of charge (1) If the sphere carries (+ ) charges, repulsion occurs between the sphere and the rod ✓ (2) Attraction exists between unlike charges. 21. C ✓ (3) Attraction exists between a charged body and a neutral body. At the centre, the forces due to the two(+) charges on the point charge C balance each other while the forces due to the two(-) charges on the point charge C also balance each other, thus resultant force on C is zero. 16. B (3)' (-) charges are induced on the sphere at the side near the rod while(+) charges appear at the far side 22. Suppose the three spheres are A, Band C such that A is uncharged, Bis positively charged and C is negatively charged. (2)' electrons flow from the earth to the sphere to neutralize the(+) charges (l) : the finger must be removed first before the removing ofthe charged rod a, A and B attract each other since a positively charged body would attract a neutral body. A and C attract each other since a negatively charged body would attract a neutral body. (4) : after the rod is removed, the sphere becomes (-) charged. ® Band C attract each other since a positively charged body attracts a negatively charged body. Thus, one sphere is uncharged and the other two caey unlike charges. 17. A When the charged rod is brought near .X, (+) charges are induced onX and (-) charges are induced on z. 23. D After Yis earthed, only the induced(+} charge remains on the left side ofX due to the attraction by the(-) charged rod. ✓ (1) Two balls carrying unlike charges would attract each other. Z would become neutral as the negative induced charges would flow to earth during earthing. ✓ (2) A ball carrying positive charge would attract an uncharged ball by induced charge. ✓ (3) A ball carrying negative charge would attract an uncharged ball by induced charge. 18. A a, presence of positively charged rod ⇒ (-) charge is induced on X while (+) charge is induced on Y "' 24. B Xis earthed momentarily ⇒ (-) charge on Xleft but (+) charge on Y is neutralized by electrons from the earth ✓ Attraction force exists between two opposite charges. (1) <l) The charged rod is removed ⇒ the (-) charge onX is then shared between Xand Y No electric force exists between two uncharged objects. (2) © Two spheres are separated ⇒ bothX and Ybecomes negatively charged ✓ A ruler carrying charge would attract uncharged paper scraps by induced charges on the paper scraps. (3) DSE Physics - Section D : M.C. Solution PD-EMl -MS/05 DSE Physics - Section D : M.C. Solution PD-EMl -MS/06 EMl : Electrostatics EMl : Electrostatics 25. A C ✓ ( !) Since repulsion exists between P and Q, they must carry like charges. The sphere carries (-)-charge ⇒ moves towards and touches (+) plate first X (2) Since attraction exists between R and S, It then shares some (+) charge and moves towards and touches the opposite (-) plate they may carry unlike charges OR one of them carries charge but the other is neutral. :. The sphere oscillates. X (3) Even P and Q carry different amount of charges, same force would exist between them. 32. C 26. D ✓ (!) Since the strip is deflected towards the positive plates, the strip should cany negative charges. As the .&field is in downward direction The negatively charged particle experiences an upward electric force (F = - q E) ✓ (2) ByE=� :. dt ⇒Et :. deflectioni d Thus, the particle accelerates in upward direction. X (3) E-field is constant within 2 charged plates, thus there is no change in deflection of the strip. 27. D 33. D Downward weight =Upward electric force from electric field mg= qE = q! E= f. = d . 03 (4 5x1 ) (15xl0"3) = 3xl06 V m (10) = (1.6 X 10-19) X (2xIO ) l :. m = 6.4 x 10-16 kg F = q E = (1.60xl0-19)(3x10 ) = 4.8x10-1J N 6 (0.05) .Sxl0-13 - '1 F 4 S.3 x10 ms-2 a =;; = 9 .llxl0-31 - 28. C ✓ (!) By U=qV :.U=(lC)x(IV)=lJ 34. C ✓ (2) By F= qE :. F= (lC)x(lVm-1) = lN Case I: Two charges areofthe same sign, i.e. (+5Q) and(+lQ). X (3) Charge on 1 mole of electrons = 6.02 x 1023 x 1.6 x 10-19 C = 96320 C ;,; I C After sharing, they become (+3Q) and (+3Q). = (SQ)Oq) = (3Q)(3�) ,; F, 4m: 0 r 4,rs 0 r 29. D :. Fi:A = S:9 ✓ (!) After touching (+)-plate, it carries(+) charge. After touching {-)-plate, it carries (-) charge. Case 2: Two charges are ofthe opposite sign, i.e. (+sQ) and (-lQ). ✓ (2) d1' ⇒ E.J, (by E =!:::,) ⇒ pJ, (by F=q E) ⇒ a J. (by a=!..) ⇒ frequency of oscillation .J, d m After sharing, they become(+2Q) and (+2Q). ✓ Carrying (+)-charge to (-)-plate ⇒ current flows in clockwise direction Q Q (2Q)(2QJ (3) F. = (S )O z ) F. = ' 4m:.r 2 4m.r z Carrying (-)-charge to (+)-plate � current flows in clockwise direction :. Fi:F.:i.=5:4 30. D 35. B Let the length of the square be r. Since the electrostatic force is attractive, X and Y carry unlike charges. Distance betweenXand Zis ✓2 r. Let the charge carried byXbe +Q and the charge carried by Ybe -Q. For sharing of charges, Qi + Q2 = Q + Q where Q is the final charge at each of the two spheres. Since the net force onXis to the left, thus the upward force by Y is balanced by the downward component of force by z AfterZtouches.X,Xcarries +½ Q andZcarries +½ Q. 2 Fz cos 45 ° = Fy .-. Q(l) ° I ( ) I .-. Q=2✓ C AfterZtouchesY,Ycarries -¼Q andZcarries -¼Q. 4n:sJ/2'rf 7z = 41ts0 ? Since the electric between% and 2 is attractive :. Z is(+) Electrostatic force : p = Qi Qi 4m: 0 r2 DSE Physics - Section D : M.C. Solution PD-EMl-MS/07 DSE Physics - Section D : MC. Solution PD-EM1-MS I 08 EMl : Electrostatics EMl : Electrostatics 36. B 40. C (1) After the plates are disconnected from the supply, charges on the plates and thusE-field are unchanged ( E = K_ = 3000) = 2xllY vm-1 Th.us the electric force is increased by F = qE as q is increased. The oil drcp then bas a net force. d (0.015) (2) Increasing the p.d. between the plates would increase the electric field by E = VI d. Bymg=qE 15 :. (9.6 x 10- ) (10) = q (2 x 10 ) 5 q = 4.&x10-19 c Thus the electric force is increased by F = q E as E is increased. The oil drop then bas a net force. To balance the downward weight, the electric force F must be upwards. ✓ (J) Moving the plates further apart decreases the E-field by E = VI d. Since the Wl"ection ofE-:field is vertically downwards, the charge is negative. The electric force may then remain unchanged by F = q E as q is increased but E is decreased. Thus, the charge carried by the oil drop is - 4.8 x 10- 19 C. The unchanged electric force then balances the weight of the oil drop by q E = mg. 41. A 37. B The positively-charged rod is brought near X X: negative Y: positive Since poinJ:Xhas the same distance as the point of 72, the electric field at Xis 72. Xis earthed momentarily X: negative Y; uncharged Distance of point Yfrom +Q is .j(3) 2+ (1) 2 = -J1o. The charged rod is removed X: negative Y: negative Electric field; E = _Q_ 4:rcs0 r2 42. A ✓ (1) The mid-point Yis a neutral point, where the electric :field due to the two charges balance each other. Thus, electric field obeys inverse-square law, i.e. E eel_ ✓ r' (2) Since the left sphere is closer to X, the negative charge is attracted by the left sphere and thus the net electric force is towards the left Elccttic field at Y = 360 x _l_ = 36. Since the right sphere is closer to Z, the positive charge is repelled by the right sphere (3) (✓IO )' and thus the net electric force is towards the left 38. B 43. D (1) They may both carry positive charges OR both carry negative charges. ✓ Some induced negative charges appear at the left side (1) (2) The charge on X may be greater OR smaller than that on Y. and induced positive charges appear at the right side of the sphere. Attraction force then exists between the positive charged rod and the negative induced charges. Ho wever, the forces between them are equal and opposite since they are action and reaction pair. ✓ ✓ (2) After touching the charged rod, the sphere shares some positive charges from the metal rod (3) Since the angle Bis smaller, thus the weight ofXis greater. and is repelled away. 39. C ✓ (3) The sphere is :finally positively charged by sharing. A X B y 44. C +Q -2Q ✓ (1) Electric force exists between the induced charges in the papers and the electric charges in the ruler. By E=-Q- , ✓ 4:n:a,, r1 (2) Since both positive and negative charges are induced in the paper, the paper remains neutral. E-field depends on the charge Q and distance r. • (J) Since the two forces are action and reaction pair, they should be equal in magnitude. At point A, charge at Xis smaller and distance is closer, charge at Y is greater but distance is longer, thus Ex= F}y. 45. A At pointB, charge at Xis smaller and distance is closer, charge at Yis greater but distance is longer, thus Ex= By. The electric field due to the upper charge is towards the left. There are 2 points with magnitude : Ex= By. The electric field due to the lower left charge is upwards. At point A, Ex is towards the left butEv is towards the right, thus the resultant field is zero. The resultant of these two fields points towards direction 1. At pointB, Ex is towards the right and Ex is also towards the right, thus the resultant field is not zero. The electric field due to the lower right charge is along direction 4, There is 1 point with zero resultant field. however, this field is weaker than the resultant of the other two, thus the overall resultant field is along direction 1. DSE Physics · Section D : MC. Solution PD-EMl-MS/09 DSE Physics · Section D : M.C. Solution PD-EMl-MS/10 EMl : Electrostatics EMl : Electrostatics 46. B 52. D (I) rt ⇒ p-!, ✓ (I) Two balls canyingwilike charges would attract each other. ✓ (2) A ball carrying positive chaige would attract an .mcharged ball by induced charge. ✓ (2) AtpointD, E-field due to the positive charge points to the right ✓ (3) A ball carrying negative charge would attract an uncharged ball by induced cbarge. and that due to negative charge points to the left. As the negative charge is nearer to D, the resultantE-fieldpoints to the left. 53. B As the - Q is moved nearer toD, E-field due to -Q further increases, and the resultantE increases. Since pointXhas the same distance as the point of 72, the electric field atXis 72. (3) At the mid pointB, the direction ofE-field due to both +Q and-Qare towards the right, Distance ofpoint Yfrom +Q is ✓(Jf +(1) 2 = ✓JO. thus, it cannot be a neutral point Since electric field obeys inverse"square law, [Note that there is no neutral point in this situation.] 47. D F = Q1 Q2 "" (l.5xl0-l7)(32xl0-l9) 2 4.32N 4,i:e r 41t(8.85xl0-12)(1.0xI0-13 )2 Electric field at Y = 360 x _I_ = 36. 48. C (Ml' E a __Q_2 =� 2 41te0 r 41t&0 r 54, D Assume that the three charges are allpositive (it is arbitrary, same result obtained if assumed negative). . . 49. D The tfuection ofE,.field by a positive charge is away from the charge. • q, ✓ (!) The density of electric field lines represents the strength of the electric field. X qz q1 E2 E As the field lines atZis closer, E-field strength atZ is greater. � E, ✓ (2) Negative charged particle experiences an electric force opposite to theE-field AtpointX, the electric field due to q1 and (ft are in opposite directions and caned each other, Thus, electric foroe on the negative charge points towards the left along the tangent of field line. the net £.field is E3 and directed towards the left ✓ (3) Electric field lines at Yis closer than thatat2; thus the electric field strength at Yis greater, At point Y, the electric field due to the three charges are all towards the right, therefore, a charge would experience a greater force at Y, by F= q E. thus the resultant E-field is rightwards, therefore, the direction of£..field atX and Yare in opposite directions. so. B The magnitude of E3 are the same atXand Y, but there areE1 andEz in addition., thus the resultant E-:field at Y is greater than that atX ✓ (I) Since the field lines are directed away from the charges, the two charges are positive. ✓ (2) As the neutral po.int is further away from P, the charge Pis greater than that of Q. 55. D ' (3) The two forces are action and reaction pair, they must be equal in magnitude. W X Y E2 Z E1 ----------1-----------©---r----- --1-----0 ·---+-'+-• M +2Q -Q 51. B ' (!) Gain of KE does not depend on the mass. The electric :field due to a (+) point charge is away from the charge. The larger the mass, the smaller the speed, but the same KE. The electric field due to a(-) point charge is towards the charge. ' (2) For cQilStant voltage between the two parallel plates, At Z, the field due to +2Q is E1 while that due to -Q is Ei, the gain of KE depends on voltage only but not affects by the separation between the two plates. and they are in opposite direction, thus they may be balanced to give zero resultant field, that is, the neutral point. ✓ (3) Gain of KE = loss of electric PE = q V. [ Note that W cannot be a neutral point as theE-field due to the greater charge 2Q must be greater since it is closer.] The greater the voltage V, the greater the gain of KE. DSE Physics - Section D : M.C. Solution PD-EMl-MS/ 11 DSE Physics - Section D : M.C. Solution PD-EMl-MS/12 EMl : Electrostatics EMl : Electrostatics B 6i. D Since P and Q repel, they must catt}' like charges. Electrostatic force: F = Qi Qz 41t&., r2 Since R and S repel, they must cacy like charges. A. To give zero resultant force on 0, the sign of Q1 and Q,. should be opposite. Since Q and R attract, they IllUSt caey 'Unlike charges. (l) Pand R must cany unlike charges, tlms they cannot be both negatively charged. B. Distance of Q1 from Q:; is two times that of Qz from 0, thus the magnitude of the charge of Qi should be 4 times as that of Qz, not 2 times. (2) Q and S must cany unlike charges, thus they cannot be both positively charged. ✓ C. To give zero resultant force on Q1, the sign of Qz and (23 should be opposite. (3) P and S must cany unlike charges, thus P may be positively charged and Smay be negatively cllarged. ✓ D. Forces between Qi and Q:; is tepulsive with magnitude : F1 (4)(4) 41t&. (2r)2 57. C Potential difference between the thundercloud and the ground (assume that theyform.2parallel plates) Forces between Qz and Q3 is attractive with magnitude: F1 = � 41tf: 0 (7)2 9 V =Ed"" (3 x 106)x(500) = 1.Sx 10 V As Fi = Fi, the resultant force on Q; is zero. Energy released : 1 U= QV= (20)(15x1G9) = 3xl0QJ 62. B Order ofmagnitude ofthe energy released = 10 10 J Due to the induced charges, a neutral ball and a positive charged ball would attract each otbct. Due to induced charges, a neutral ball and a negative charged ball would attract each other. 58. D The deduction should be : Before touching, electrostatic force between the two spheres : (D one ball carries positive charge F • (2Q)(6Q) • l2_g__ <J) one ball carries negative charges 41te0r2 4ite0r 2 <l) one ball is uncharged (neutral). After touching, the net charges are: (6Q) + (-2Q) = +4Q 63. D This charge is then shared betweenXand Y, each has +2Q. After touching, electrostatic force between the two spheres : F' • (2Q)(2Q) • 4_g__ • �F 41t&0,-2 4,u.-072 3 X The electrostatic forces betweenXand Y are repulsive as they carry like charges. Assum:e the neutral point Pis at a distance ofx at the right side of Q2. Since Q 1 is negative, the electric field Bi due to Qi is towards the left. 59. C Since Qi is positive, the electric field E2 due to Qz is towards the right. When the positively charged rod is brought near X,Xis negatively charged and Y is positively charged. To be the neutral point, the two electric fields must be equal and opposite. WhenXis touched by the finger,Xis still negatively charged but Ybecomes uncharged. :. X = 3 When Y is removed, Xremains negatively charged and Yremafus uncharged. When the charged rod is removed, Xre.ma.ins negatively charged and Y remains uncharged. The neutral point is atZ. 60. D 64. D Since the electton carries negative charge, the dttection of electric :field should be from Pto Q. There are two points that the magnitude ofthe electric field due to the two charges are equal. For the same electric field (both magnitude and direction), the point must be at the right side of +Q. By F = qE Let the point from O be x. :. (8.0 x 10-18) = (1.6 x 10-� E Q ••• X = 30cm :. E = S0NC-1 41tE:., -x2 DSE Physics - Section D : M.C. Solution EMl : Electrostatics PD-EMI-MS/13 I DSE Physics - Section D : Question EMl : Electrostatics PD-EM! -QI 01 II 65. B Thefollowinglistofformulae maybe found useful: (!) Since the electrostatic forces between the two spheres are repulsive, both spheres cany like charges. - F- Q,Q, 41te0 r' However, both spheres may carry positive crulrges OR both may carry negative charges. Coulomb's law (2) The arttOUllt of charges on the two spheres may NOT be the same. Electric field strength due to a point charge ✓ (3) The electrostatic force F acting on the higher sphere is upwards that balance its downwards weight mg. :, mg=_g&_ 2 4ne0 d Electric field between par.ill.el plates (numerically) Thus, the separation d depends on m. Use the following data wherever necessary : 66. D Acceleration due to gravity g = 9.81ms~2 (close to the Earth) By E =--Q- 4xe0 r2 Charge of electron e = l.6x10-19 c Elec'.ron rest mass m. = 9.11 x 10-31 kg Thus, E must be positive and tends to zero as rtends to infinity, therefore, option A and B must be incorrect. Permittivity offree space Since the charge Q is placed at- d, the electric field must exist starting from - d, thus option Dis correct. Part A � HK.CE examination questions 1 1. < HKCE 1985 Paper I- 9 > (a) A girl, after combing her hair on a dry day, holds the comb near small pieces of paper. What will be observed if the comb is made of (i) plastic, and (ii) aluminium ? Explain briefly in each case. (4=b) I\ (b) Two similar charged metal-coated balls, A and B, are suspended from two i.nsulating threads as shown in the figure. (i) Draw on the diagram all the forces acting on the two balls. (n) Ifthe ball A is earthed by touching. what would happen to the two balls ? Explain briefly. DSE Physics - Section D : Question PD-EMl-Q/02 DSE Physics - Section D : Question PD-EMl- Q/03 EMl : Electrostatics EMl : Electrostatics ,� 2. <BKCE 1987 Paper I- 9 > 4. < HKAL 2011 Paper I - 7 > E.H. T. via an ammeter as shown The below figure shows two aluminium. foils held by plastic clips and a negatively charged plastic block. They are used for A small conducting ball is placed midway between two parallel metal plates connected to an charging the aluminium foils by induction. in the Figure. p1'stiobln,kQi aluminium foil (,) Descnbe the steps taken in charging the aluminium foils. (3 marks) E.H.T. (b) What type of charge is induced on the aluminium foils ? (1 mark) (a) State how to make the ball acquire positive charges. (1 mark) (,) Explain briefly why the clips should be an insulator but not a conductor in this experiment. (2 marks) Part B : RKAL examination questions 3. < BKAL 2006 Paper I - 4 > (b) After the ball acquires positive charges, explain why it can shuttle continuously between the two plates. In a vacuum, a beam of electrons with an initial horizontal velocity enters midway into a region of electric field between two horizontal square metal plates as shown in the figure below. A p.d. of 320 V is applied across the plates and the separation between them is 1.6 cm. ,_L 116= r 320 V clootron •._ T plates (c) State and explain how the average current registered by the ammeter is affected if the separation of the two metal is decreased. (3 marks) {a) Find the electric field strength between the plates. (2marks) (b) The electron beam reaches one of the plates. Sketch in the above figure the path of the electron beam between the two plates. (Neglect the weight of the electron..) (2nwks) DSE Physics - Section D : Question PD-EMl -Q/04 DSE Physics - Section D : Question PD-EMl-Q/05 EMl : Electrostatics EMl : Electrostatics Part C : HKDSE examination questions 6. < UKDSE 2013 Paper IB-11 > Figure (a) shows two identical small metal spheresX and Y suspended by insulating -9threads of the sam� length. Each sph� ( C). The separation d of the spheres is s. < BKDSE Practice Paper IB � 8 > has amass of LO x 10-s kg and each carries a positive charge of3.l nC 1 nC = 10 p As shown in the Figure, two lar ge vertical parallel metal plates, each in a slotted base, are placed on a polystyrene tile. The 10 cm. The size of spheres is negligible compMed with their separation, therefore they can be treated as oint charges. plat.es are connected to the positive and negative tenninals of an EHT supply respectively. The plates' separation d= IO cm. Truce_!_,,, 9xt0 Nm C . 9 2 -2 41te0 m"'1 plate Diagram NOT drawn to scale Figure(a) X cf Y EHT supply <:--------> d=l0cm polystyrene til• (a) Find the angle between the threads. A small charged ball is suspended by a n ylon thread and is placed midway between the plates. The thread makes an angle 0 to the vertical when the ball is in equilibrium. (a) By using a :free--body diagram, draw and name all the forces acting on the charged ball. Also indicate in your diagram the direction of the electric field between the plates. (3 llllll'ks ) (b) Point P is vertically below the fixed point O and it is 10 cm from each sphere as shown in Figure (b). (i) Indicate the direction of the resultant electric field at P due to these two charged spheres. (1 mark) (b) (i) Express tan 0 in terms of the electric force F acting on the hall and the wei ght W of the ball. (1 mark) Diagram.NOT drawn to scale Figure(b) (ri) Given that the mass of the ball is 0.07 g. When the voltage between the plates is 4000 V, 0 = 2°. Estimate the magnitude ofthe charge carried by the ball. Assume that the electric field between the plates is unifurm. ( 3 """") (c) Using the setup in the Figure, suggest a simple method to test whether the electric field between the plates is uniform. (3 marks) (ii) A neutral metal sphere of finite size is now placed at P. State whether the separation dwould increase, decrease or remain unchanged due to the presence of this sphere. (1 mark) Separation d ....... ______ DSE Physics • Section D : Question Solution PD-EM1 -QS / 01 DSE Physics - Section D : Question Solution PD-EM1 -QS / 02 EMl : Electrostatics EMl : Electrostatics HKEAA's Mar1cin&: Scheme is prepared for 1he markers' :mfercnce. It should not be regarded as a set of model answers. 1 Students and teachers who me not involved in the marking process are advised to inteipret the Markixlg Scheme with care. 3. (b) Question Solution 320 V ol,ctrnn :_:::::::> 11.6= 1. (a) (i) Small pieces of paper are attracted by the comb and are found on the comb l- [!] T Since the plastic comb is an insulator, charges produced by robbing remain on the comb [!] (ii) Small pieces of paper are not affected and stay at the original places [!] [!] < The path bends upwards > Since aluminium is a conductor, charges produced by rubbing will be conducted a:way. [!] [!] < The path is a curve > (b) (i) T T [!] 4. (a) Let the ball touch the left plate to share some positive charges. F'+---\ [!] j--+p (b) The ball is repelled by left plate and attracted to the right plate. The ball then aequires negative charges when touching the right plate and the process repeats. [!] Hence, the ball shuttles between the two plates. w w (c) As the plate separation d decreases, the electric field between the plate increases ( E = VI d). [!] < weight of the two balls marked correctly> [!] Therefore, electric force on the ball increases. [!] < tension of the strings marked correctly> [!] The acceleration of the ball increases and thus the average CU1Tent increases. [!] < electrostatic force between the two balls marked correctly > [!] (u) Both ball.A and ball B fall, [!] touch and then separate again [!] 5. (a) T (tension) �"--�-- Since charges in ball A is conducted away, it is attracted by ball B [!] When it makes contact with ball B, it shares similar charges and repels away. [!] direction of electric field 2. (a) Place the aluminium foils near the plastic block. [!] w(weight) Touch the foil momentarily with a finger. [!] [!] < Weight and tension correctly drawn with correct name > Then remove the block. [!] [!] < The electrical force correctly drawn with correct name > < Direction of electric field correct > [!] (b) positive charge [!] [!] (c) Iftbe clip is a conductor, the induced charge would escape (b ) (i) tanB • f_ through the clip and the band. [!] w [!] (ii) For parallel plates: E = !:. = 4ooo = 40000 V m-1 [!] d 0.1 3. (a)E=� tan0 = !_ == qE d W mg 320 q•(40000) [l] [!] 0.016 tan2" == (0.07 xio-')(9.81) = 2xl04 Vm-1 (OR 20000NC-1 ) [!] [!] :. q = 6.0ox10-10c DSE Physics - Section D : Question Solution PD-EMl-QS/03 • Hong Kong Diploma of Secondary Education Examination EMl: Electrostatics : Physics - Compulsory part (;1,if<Jl,l-) , Section A-Heat and Gases (�'f"liUll:) , 1. Temperature,Heat and Internal energy (m.&, ;;,,;i;�R�) 5. (c} Fix the plates separation and the output voltage of the EHT Supply. [!] 2. Transfer Processes (1¥.#:fJ:i&.fl.) Move the polystyrene tile so that the ball is placed in different positions in the space between the plates. 3. Change of State (%.@:�iltyt) [!] 4. General Gas Law (-ti&�J'llt;t.#) The angleBshould remain the same if the electric field between the plates is unifonn. [!] 5. Kinetic Theory ( '.S,-"7'.i{�rt,i) SectionB -Force and Motion (:h:ft!Jl10) 1. Positionand Movement (1ir.1f.'f":11*-i) 6. (a) 2. Newton's1aws(4,<ll1i::t.#) T 3. Moment ofForce (iJ#!) ( 4. Work,Energy and Power (,fj:J:/J � j�:1,:;fcr.;&*) 5. Momentum(Z'l:ft) 6. Projectile Motion (&:lti'E:ti'J) 7. CircularMotion(l!)J;ll�!») F+- 8. Gravitation ('iii]) Section C- Wave Motion (ii:.111) w 1. Wave Propagation (/&'.{t,i;J!til!) 2. WavePhenomena(JBtj).lJl.$.) .--9 2 3. Reflection and Refraction ofLight ( 16ft:l �MA:brM) F = �2 = (9 x 109) x (3.Ixl0 ) = 8.65 x lO�N [I] 4. Lenses (iS.�) 4ite0 r (O.lo)2 5. Wave Nature ofLlght (:J'e.�ii.:ti'J�·!t.) "" 5 6. Sound(tt) W =mg= (LO x 10 ) (9,81) = 9.81 x I<r-5N Section D - Electricity and Magnetism ( 11!::fl'.fit) ResolvethetensionT: TsinB=F and TcosB= W 1. Electrostatics (ff-1!!:�J!,) 6 2. Electric Cimlits ( 'l!t.'13-) :. tanB = !_ "" 8.65xI0-""5 [!] 3. DomesticE!ectricity(Ull!'ilt) W 9.81xl0 4. MagneticField(:qt.¼,Jt) ° :. 0 = 5.04 5. Electromagnetic Induction ('it.i;;lt� .(Ji) Angle between the threads = 2B = 10,l 0 6. Alternating Cmrent ( 5c,,m.'1ft) [I] Section E- Radioactivity and Nuclear Energy (:tk¼tJJ!.�;f";ft1!5) (b) (i ) 1. Radiation and Radioactivity ( .tiMt'f�<l'l:.M JJL ,t..) 2. Atomic Model (,IJT.fU:D 3. Nuclear Energy(#.!:�) Physics -Elective part (;!if'Jl�') Elective 1 -Astronomy and Space Science (�X.-$:Jiu,tt;i<;..f'I-,$) 1 1. The universe as seen indifferent scales (;;i;!IIJ'!E. M-iUtrl!ll�'iliilbtt.) 2. Astronomythroughhistoly (;t:si:.,:!j!,l!ll-§--1..t.) 3. Orbital motions under gravity ( Jii1Tft:l.$1t,i!ifitb) 4. Stars and the universe (•/Y.£.'fu�ii) Elective 2 - Atomic World CW. T-fr.ff..) L Rutherford's atomic model (11£�-f.T-lJt�) 2. Photoeleetric effect (/6 '!ltl!tli) 3. Bohr's atomic model ofhydrogen (Jk.ril 18i.�T-ilt�) 4. Particles or waves ($.T�it) 5. Probinginto nano scale Cm�#i'*�.J}) Elective 3 - Energy and Use of Energy (tl'§it'f":ll.i.!f.�{j!_lfi) 1. Electricityathome(�.lk.lli1!!:) < direction ofE: vertically downwards> [!] 2. Energy efficiency in building ( J:l!A� � �Si.!Mt 41) 3. Energy efficiency in transportation c�.ni-�Mi �Si!F.�!fl:) (ii) Sopa,,tinn d , d0<,,e,,., 4. Non-renewable energy sources (;;i;-r�i.�i.'l'i) [!] 5. Renewable energy sources (".f .,il}i.�6�) Elective 4- Medical Physics ( f} ,!f:4v,i lf.!J/,) 1. Making sense ofthe eye (!l!HS@li. if) 2. Making sense ofthe ear (.lfft:lti. 'is) 3. Medical imaging using non-ionizing radiation ( -'If 11:Nt.tiM-I' *i:51l*) 4. Medical imaging usingionizingradiation ('lll:Mll#rM-&<$-JMt�) I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/Ol II DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/02 The following list of formulae may be found useful : 2. < HKCE 1980 Paper Il- 38 > Resistance and resistivity R ,---C'.'.:::J---{ A Resistors in series R""R1+R1 R K Resistors in parallel 1 1 1 Two identical resistors R, an ammeter, a switchK and a cell are connected as shown. When K is open, the ammeter reading -=-+- R R, R , is 1 A. When K is closed, the reading will A not change. Power in a circuit B. increase to 2 A C. increase to 4 A. D. decrease to A ½ USe the following data wherever necessary: 3. <HKCE 1980 Paper ll- 44 > Acceleration due to gravity g "- 9.81 ms-1 (close to the Earth) Charge of an electron e = 1.60 x 10- 19 C Electron rest mass m,, = 9.11 X 10-31 kg 100n Permittivity offree space In the circuit shown, Vis a vol1meter of high intemal resistance and A is an ammeter oflow internal resistance. What is the voltmeterreading when (a) switch K is open, and (b) switch K is closed ? Kopen Kclosed Part A: HKCE examination questions A OV ov 1. < HK.CE 1980 Paper 11- 32 > B. ov 2V C. 1V IV In the circuit shown, the battery has an e.m.f. of 6V with negligible internal resistance. Four resistors are connected to the D. 2V ov battecy as shown :in the figure. 40 p "' 4. < HKCE 1981 Paper n- 25 > Suppose that it takes� to boil a kettle of water. If the beating coil of the kettle is shortened to half its original length and the supply voltage remains unchanged, then to boil the same amount of water will take A. 16min. B. Smin. 40 C. 4min. Q D. 2min. 5. < HKCE 1981 Paper n- 29 > 6V What is the potential difference between points P and Q 1 A 1V In the circuit shown, what is the power dissipated in the 4 .Q resistor ? B. 2V A. o.sw B. LOW C. 3V C. I.SW D. 4V D. 2.0W DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/03 11 I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD -EM2 -MI 04 II 6. < HKCE 1981 Paper n - 28 > 10. < BKCE 1982 Paper ll- 27 > R, R, A A, sooon �---1 B In the circuit shown, the cell has negligiOle intemal resistance. Ifthe lamp LJ bums out, then A. L 1 becomes brighter. In the circuit shown, ammeter A1 reads 2 mA and ammeter Ai reads 8 mA What is the voltage across AB? B. k becomes brighter. A lOV C. L 1 becomes dimmer. B. 40V D. L1 retains the same brightness. C, 50V D. lOOV 11. < HKCE 1982 Paper Il- 30 > 7. <BKCE1981PaperII-27> Suppose you were given four similar lamps and a battety. Which of the follo wing ways of connecting the lamps to the battezy would give the maximum brightness overall ? C rn rn D A. a 2Q - A rn rn B The diagram shows a network of resistors, where the resistance of each resistor is 2 n. What are the equivalent resistances across AB and AD respectively ? AB AD C. D. A. I.67 n l.OOQ B. 1.67Q 1.67 n C. 1.670 3.670 D. 2.son 1.oon 8. < BKCE 1982 Paper II- 31 > In the circuit shown, the cell has negligible internal resistance. R Toe two resistors Rare identical. If the power dissipated in the circuit is P when K is open, find the power dissipated when K is closed. A. ¾P R K 12. < HKCE 1982 Paper Il- 33 > B. ½P C. 2P D. 4P 9. < BKCE 1982 Paper 11-1 > Which of the following are vectors? {I) weight (2) charge In the given circuit diagram, the battery has a _voltage__Q.f -� .Y. and negligible internal resistance. The three resistors are (3) voltage identical and the voltmeter has the same resistan� as each resistor. What is the reading on the voltmeter? A (1} only A l�V B. (1) & (3) only B. 1.2 V C. (2) & (3) only C. 1.5V D. (1). (2) & (3) D. 2.0V I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/05 11 I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/ 06 II 13. < HKCE 1983Paper II - 27 > 17. <HKCE1983Paperll-30> 6V III ,-------, I I I I-----, 3A lA 2A A &· In the circuit shown, what is the current passing through the ammeter A ? In the circuit shown. the resistances ofR1,& and & are all equal to 2 n. The power dissipated by& is A. 0A A 2W B. IA B. 4W C. 2A C. 6W D. 4A D. SW 18. < HKCE 1984 Paper 11-12 > 14. < HK.CE 1983Paper 11- 32 > An immersion heater of resistance SO n raises the temperature of 1 kg of water by 20°C in 3 minutes, the voltage supply The resistance of a given conducting wire may be increased by being 200 V. \Vhat would be the energy wasted? (1) · decreasing the :radius of the wire. (Specific heat capacity of water= 4.2 kJ kg"1 0 C-1 ) (2) increasing the length ofthe wire. (3) winding the vvire in the form of a coil A 0.44kJ A. (1) only B. 2.32kJ B. (1) & (2) only c. 44kJ C. (1) & (3) only D. 60kJ D. (1), (2) & (3) 19. < BKCE 1984 Paper II - 32 > ·l � HKCE 1983Paper 11- 28 > The diagrams below show three possible arrangements of four identical resistorsR. JWhen connected in series man electric CII'CUlt, the power diss1patcd m two resistors R1 and R:.z lS in the ratio of 1 : 4. What will be the ratio of the power dissipated inR1 and& when they are connected in parallel? (a) R A. 1 :2 B. 2 :1 X�Y c. 1 :4 D. 4:1 ( b) R R 16. <BKCE1983PaperII-31> X�Y (o) R s X y In the above circuit, A1, A2 and AJ are ammeters of negligible internal resistance. What will happen to the readings of the anuneters if the switch Sis closed? List the arrangements in order of�equivalent resistance, as measured betweenX and Y. Reading of At Reading ofAi Reading of .43 A. (a), (b), (o) A decreases increases becomes zero B. (b), (o), (a) 13. increases decreases decreases C. (o), (a), (b) C. unchanged increases becomes zero '"D. unchanged decreases increases D. (o), (b), (a) l ti = _ == ==D::: EM2S:::E:::Phy=::: sics=-:::S:::ee1l : Electric :::":::on:::D=: M c Crrcuits . . 2 = P D - E M =- M / O 7. ::: ::: :::=== = ::: :::::: ::: ::: :::::: ::;J .. I I DSE Physics - Section D : M.C. EM2 : Electric Crrcuits PD-EM - /08 2 M 11 20/ 7< HK.CE 1984 Paper n - 33 > 24. < HKCE 1985Paper Il - 44 > I I V Which of the following will increase the resistance ofa metal wire ? (1) increasing the length of the wire (2) increasing the cross-sectional area of the wire (3) increasing the temperature ofthe wire p R A. (I) only B. (1) & (3) only C. (2) & (3) only D. (1), (2) & (3) Four identical bulbsP, Q, Rand Sare connected as shown in the two circuit diagrams above. What happens to the brightness of P andR if the switches of both circuits are closed? Brightness of P Brightness of R A. decreases remains constant B. remains constant decreases C. increases remains constant D. decreases decreases In the circuit, whenK1 is closed the voltmeter reads 12 V. What would the reading be ifbothKi and Ki are closed? A. 8V 21. < HKCE 1985 Paper ll- 36 > B. 12V C. 16V D. 18V 26. In the circuit shown, all bulbs Bare identical. If ammeter A1 reads 1.8 A, what does ammeter A2 read? A 1.2A B. 0.9A C. 0.6A D. 0.3A In the above circuit A 1, /4i ancl'A3 are ammeters connected to a constant voltage source. What will happen to the readings of the ammeters if the switch Sis closed ? 22. < HK.CE 1985 Paper Il- 34 > Ai A2 Al An immer.rion heater A. talces 10 minutes to boil a kettle of water while another h�ter B takes 40 minutes to boil the same A. decreases increases becomes zero kettle of water under the same vOitage Sllppiy. If the resistance ofheatet: A is 100 .n, "what is-the resistance of heater _B � B. increases decreases decreases C. no change increases becomes zero A 500. D. no change decreases increases B. 100.Q C. 2000 27. <HKCE1986Paperil-30> D. 4000 Ammge the following circuits in ascending order of equivalent resistances : (1) (2) 23. < HK.CE 1985 Paper II- 35 > A student, who wishes to find the resistance ofa light bulb when � connected to at:� !J�, incorrectly connects a�cal v.o!Eueter and a ;practii;_al ammeter as shown. What woii1:o'bethe (3) most probable outcome -Of his error? >------< A ,_____, A. The voltmeter would indicate zero voltages. o---+--{�J--+---. B, The ammeter would bum out A. (3), (2). (1) B. (1), (3). (2) C, The light bulb would bum out. C. (2), (3), (1) D. Both the ammeter and the voltmeter would bum oul D. (2). (1). �) I DSE Physics - Secti.on D : MC. EM2 : Electric Circuits PD-EM2-M/09 I I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/ 1011 28. < HKCE 1987 Paper II - 28 > 32. < HKCE 1988 Paper n- 27 > What should be the potential difference between P and Qin the cixcu.it shown 7 p A. 3V B. 6V C. 9V Q D. 12V 33. < HKCE 1988 Paper n- 30 > Four identi.callampsP, Q, R andS are connected to a battery as shown above. Ifiamp Pis blown, which of the followlng would happen ? In the circuit shown. which ofthe switches should be closed in order A. Lamp R becomes brighter. to get the maximum brightness in lamp L? B. Lamp Q becomes brighter. A. Xonly C. Lamp S becomes brighter. B. Yonly D. Lamps Q and S :remain at the same degree ofbrightness. C. Z only D. XandYonly 29. <HKCE 1987 PaperII-32 > 34. < HKCE 1989 Paper ll- 34 > Two copper wires, A and B, of the s� have the ratio of� ofj,,1 Assuming the cross-sections are unifonn, what is the ratio ofthe resistance ofA to that ofB? A. 2:3 p Q R s B. 3:2 C. 4:9 The above circuit shows two resisrors R1 and R;. connected in se_ries'to a battery. The resistance of R1 is greater than that of D. 9:4 ,&. The ends of the resistors are markedP, Q, Rand S. Which of the graphs best shows how the potential V varies along PS? � 6-rr b_ � A. B. C. D. 35. < HKCE 1989 Paper II- 31 > In the circuit shown. resistors A, Band Care identical. WhenK is open, the power dissipated by A is P1. When K is closed, the power dissipated by A becomes P2. The ratio Pi : P2 is equal to A. 3:2 P Q R S P Q R S P Q R S B. 2: l P Q R S C. 9:4 30. < HKCE 1987 hper 11- 30 > D. 4: 1 In the circuit shown, all resistors are the same. If the current passing through point X is 1 A. what will the current delivered from the battery be ? R 36. < HKCE 1989 Paper II- 38 > lA A. lA X B. 2A C. 2.SA A D. 3A R V }-+=:::i-....J 31. < HKCE 1988 Paper II- 26 > K In the circuit shown, the energy required by an electron to travel p 2Q fromQ to P through Xis Et and that through Yis £2. vVhich of Q In the circ-ujt above, the two resistors are identical When the switch K is closed, what happens to the readings of the X the following is true 'I ammeter A and the voltmeter V? 4Q Reading of ammeter A Reading of voltmeter V A. E1 = 4E2 y B. Et = 2£2 A. increases decreases to zero C. E1 = Ez B. decreases decreases to zero C. decreases decreases D. 2E1 = Bi D. increases decreases 1 37. DSE Physics - Section D : M.C. EM2 : Electric Circuits < BKCE 1989 Paper II- 33 > PD-EM2-M/ll I I 41. DSE Physics - Section D : M.C. EM2 : Electric Circuits < HK.CE 1991 Paper Il- 30 > PD-EM2 -M /1211 A B C D '---------<,1�-...,,...,,_--1 In the above circuit, P, Q and R are identical resiston. Which of the following is true when switch Sis closed ? A. The power output from the battery increases. B. The voltage across P remains unchanged. In the circuit shown, a 4 n resistor is tobe connected to two of the terminals A, B, C andD to give the greatestbrightness in C. The cime:nt tbroughQ remains unchanged. the lampbulb. Which connection should be made? D. The currentthroughP decreases. A. acrossA.B B. acrossBC C. across CD 42. < HKCE 1991 Paper II - 33 > D. acrossAD In the circuit shown, what are ·the readings of voltmeters Vi and V2 if switch Sis closed ? 38. <HKCE1990Paperll-35> Voltmeter Vt Voltmeter J'i An electric heater takes a time Ttoboil a kettle of water when connected to a 200 V source. '\Vb.at willbe the time required A. ov 2V 100 to boil the s.une kettle ofwater when the heater is connected to a 00 V source? B. ov 3V (You may assume that the resistance of the heater remains unchanged.) 1 C. IV 2V A. T/4 D. 3V ov B. T/2 C. 2T 43. < BK.CE 1991 Paper II- 31 > D. 4T The following diagrams show three networks consisting of different resistors. �----" 39. <HKCE1990Paperll-32> (1 ) ~--+�---! II: !--+--� � � (2) 10 !Mn 6V ( 3) !Mn In the circuit shown, the potential differencebetweenXand Yis A. ""'· B. LS V. C. 3.0V D. 4.SV. Arrange the above networks in descending order of equivalent resistances : A. (1), (2), (3) B. (2), (!), (3) 40. <HKCE 1990 Paper Il - 34 > C. (2), (3), (1) D. (3). (!). (2) In the circuit shown, Li ,Li andL3 are identical light bulbs. Which of the following statements is/are correct when the switch Sis closed ? 44. <HKCE 1991 Paper II-1 > (1) The brightness ofL1 decreases. Which of the following is/are vectors ? (2) L,. and Ls are of $ame brightness. (1) momentum (3) Ldsbrighterthan.Lz. (2) power (3) voltage A. (2) only A. !) only B. (3) only B. (�) only C. (!) & (2) only C. (1) & (2) on ly D. (2) & (3) only D. (2) & (3) only I DSE Physics - Section D : M.C. m.12 : Electric Circuits PD- EM M 2- /13 11 DSE Physics - Section D : M.C. m.12 : Elec1ric Circuits PD-EM2-M/14 1 Ji------. 45. <HKCE 1992 Paper II - 29 > 49. < HKCE 1993 Paper II- 29 > The potential difference between t:wo pointsX and Yin a circuit is 10 V. Which of the following must be true ? A. 1 J of electrical potential energy is transferred in passing 10 C of charges fromXto Y. �---11 B. SJ of electrlcal potential energy is transferred in passing 2 C of charges fromXto Y. C. 10 J ofelectrical potential energy is transferred in passing l C of charges fromXto Y. D. The resistance between%and Yis 10 n. A, 46. < HKCE 1992 Paper II- 31 > A,)---C=}-� L--j=:::J---{A,}------' In the circuit shown above, all resistors are identical and the ammeters are of negligible resistance. If the readings of A, }---..----J==}--r------+ ammeter A1 is 2 A, find the readings of ammeters Ai and AJ . s A, A, A. 2A 2A A, }----- -C==:J---- .J B. 2A 4A C. 4A 2A D. 4A 6A In the circuit above, what happens to the readings of the three ammeters if switch Sis closed? Ai Ai A:i """""" A. increases increases increases 50. < HKCE 1993 Paper II- 30 > B. remains unchanged becomes zero increases C. increases becomes zero Which of the following circuits can be used to measure the resiS!mC� of the light bulb? A B. �-----1111---� D. decreases increases becomes zero 47. <HKCE1992Paperll-32> A �----< V I---� Jn the circuit shown, what is the power dissipated in the 10 O resistor ? A. 0.8W C. D. B. 1.6W c. 2.4 W D. 3.6W 48. < HKCE 1993 Paper II- 32 > L, L, 51. <HKCE 1994 Paper II- 26 > A student uses an ammeter and a voltmeter to find the resistance In the circuit, L1, M. andL3 are identical light bulbs. Which of the following statements is/are true? of a light bulb. He incorrectly connects the circuit as shown. (1) Li andL3 are ofthe same brightness. Which of the following is the most probable outcome ? (2) Li is brighter thank. A The ammeter bums out V (3) The power dissipated in L1 is equal to the sum ofpowers dissipated in Li and £3• B. The light bulb burns oul A. {2) only B. (3) only C. The reading of the voltmeter is zero. C. (1) & (2) only D. (1) & (3) only D. The reading of the ammeter is zero. 52. DSE Physics - Section D : M.C. EM2 : Electric Circuits < HKCE 1994 Paper II - 28 > PD-EM2-M/15 I 56. DSE Physics - Section D : MC. EM2 : Electric Circuits < HKCE 1995 Paper II- 33 > PD-EM2-M/16 11 A, A,·'----< L-----/ V l---_J In the above circuit, all the light bulbs are identical. What happens to the brightness of the bulbs L1 , k and LJ if switch S is closed? In the circuit above, the ammeters have negligi'ble resistance. Which of the following statements are true if switch S is L, L, L, closed? A. decreases increases remains unchanged (I) The reading ofammeter A1 decreases. B. increases remains unchange d increases (2) Thereading ofammeterkincreases. v' C. decreases remains unchanged remains unchanged (3) The reading of the voltmeter remains unchanged. D. remains unchanged decreases increases A. (1) & (2) only B. (1) & (3) only �T C. (2) & (3) only < HKCE 1994 Paper II- 27 > D. (1), (2) & (3) 57, <HKCE 1995 Paperll-1 > 4<l x4" Which ofthe following pairs of physical quantities has the same units ? A. Charge and current 4!2 B. Workandvoltage y C. Kinetic energy and heat D. Force and momentum Find the p.d. betweenXand Yin the above circuit A. ov B. 1 V 58. <HKCE 1996 Paper II- 30 > C. 2V It is knovm that the resistance ofa resistor R is about 5 kn. Which of the following circuits is most suitable for measuring the D. 3V resistance ofR? The ammeter and voltmeter used are common moving coil meters. B. 54. < HK.CE 1994 Paper II- I> A, ---"II,___ --- I I 1--- Wf!ich of the following is a correct unit for the corresponding physical quantity? R Physical quantity Unit .--r----,_-1 A A. Work watt B. Electromotive force newton '---< V '-----' '----" A l--___, C, Momentum newton second D. Heat capacity joule per kilogram C. D. I 55. < HKCE 1995 Paper II- 27 > 10n p I 1----C::::J---, Q sn ,------[=}--j A, ron L--CJ----{ A, 59. <HKCE 1996 Paper II-1 > In the above circuit, the reading of ammeter A1 is 0.6 A. Find the p.d. between pointsP and Q. Which of the following expressions does not represent energy? A, 3V A. Force x displacement B. 6V B. ± x mass x (speed)2 C. 9V C. (Cwrent)2 x resistance D. 12V D. Cwrent x voltage x time I 60. DSE Physics - Section D : M.C. EM2 : Electric Circuits < HKCE 1996 Paper II- 27 > PD-EM2-M/17 11 64. DSE Physics - Section D : M.C. EM2 : Electric Circuits <HKCE 1997 Paper 11-31 > PD-EM2-M/18 y X 6Q y\---- In the circuit shown, the reading ofammeter A2 is 0.3 A. Find the reading ofammeter A1. Jn the circuit shown, X and Y are identical beaters. The ammeter has negligible resistance while the voltmeter has veiy high A. 0.75A resistance. When switch Sis closed, the ammeter records a reading but the voltmeter reading is zero. Which ofthe following B. 0.6A provides a possible explanation? C. 0.SA A. The heater Xburns out. D. 0.45A B. The heater Ybums out. C. The heater Xis short.circuited.. D. The heater Yis short-circuited. 61. < HK.CE 1996 Paper II -32 > 65. < HKCE 1998 Paper Il - 30 > �1[� 6V ---'I[>----- � 6Q R A.H=::i-. Figure(a) Figure(b) 12" In Figure (a), the ammeter reading and the total power dissipated in the two identical resistors are I and Prespectively. The resistors are rearranged as shown in Figure (b). Find the ammeter reading and the total power dissipated ii:!. the two resistors. Ammeter reading Total power dissipated In the above circuit, the reading ofthe ammeter is 0.4 A. Find the resistance of the resistor R. A. 3Q A. 2l 2P B. sn B. 2l 4P C. 6Q C. 41 2P D. 9Q D. 41 4P 66. < HKCE 1999 Paper II- 27 > 62. < HK.CE 1997 Paper II - 1 > Which ofthe following expressions represents a physical quantity which is different from the others ? A. Work / Time B. (Voltagef-/ Resistance C. Force xVelocity D. Mass x Specific latent heat of fusion 63. < HK.CE 1997 Paper II- 29 > All the resistors in the below networks are identical. (1) (2) (3) A student uses the above circuit to :find the resistance of a resistor R voltmeterreading (i.e. resistance ). ammeter reading Which ofthe following statements is/are correct? {1} The am.meter reading records the actual current passing through R. (2) The voltmeter reading records the actual voltage across R. Arrange the networks in ascending order of equivalent resistances : {3) The value ofthe resistance ofR obtained is smaller than its actual value. A. (1), (2), (3) A. (1) only B. (1), (3), (2) B. (3) only c. (2), (1), (3) C. (1) & (2) only D. (3), {!), (2) D. (2) & (3) only I 67. DSE Physics - Section D : M.C. EM2 : Electric Circuits < HKCE 1999 Paper II- 28 > I PD-EM2-M/1911 70. DSE Physics - Section D : M.C. EM2 : Electric Circuits < BKCE 2000 Paper II - 34 > 9V PD-EM2-M/201 I • I - �--<ljt---� 60'2 A - 60Q - 30Q A resistor and a bulb are connected in parallel to a 9 V battery as shown above. The reading of the ammeter is 5 A. H the power dissipated by the resistor is 18 W, find the power dissipated by the bulb. In the above circuit, the current delivered by the cell is I. What is the current passing through the 30 n resistor? A. 9W A. ½I B. 18W B. t1 C. 22.SW D. 27W C. ¼1 D. t1 71. < HK.CE 2000 Paper II- 36 > I ' 68. <HKCE 2000 Paper Il - 30 > I + I R1=6.Q 4!l p Q _fu= 12.Q Three resistors are connected to a battery as shown above. Which of the following statements is/are correct? (1) The current passing through R1 1s equal to that passing through .R;;. (2) The voltage across R1 is equal to that across k (3) The energy dissipated by one coulomb of charge passing through the 4 !2-resistor is equal to that dissipated by one coulomb of charge passing through PQ. Q R A. (3)only 1l, (1) & (2) only C. (2) & (3) only Bwb .0.. (1), (2) & (3) Voltmeter 69. < HKCE 2000 Paper II- 31 > s The above figure shows an experimemal set-up for measuring the resistance of a bulb. To which of the temrinals P, Q andR ofthe ammeter and voltmeter should each of the wires be connected 1 R 1--_.._-c':::i--{ A A, Wire (1) Wire (2) Wire (3) II R, A. p Q R j-----C_j-----, A A, B. p R Q C. Q p R R, D. R p Q '-----{C::J------{ A A, If switch Sin the above circuit is closed, which of the following statements is/are correct? 72. < lll(CE 2001 Paper II - 27 > (1) The readings of ammeters A1 andA2 are both increased. (2) The ratio of the readings of ammeters Ai and A2 is increased. Which of the following relations is incorrect 1 (3) The reading of ammeter A3 remains unchanged. A. 1 ohm (0) 1 volt per ampere (V K1) A. (I) only B. 1 watt (W) 1 joule per second (J s-1) B. (3) only C. (1) & (2) only C. 1 coulomb (C) 1 ampere per second (A s-1) D. (2) & (3) only D. 1 volt (V) 1 joule per coulomb (J C-1) DSE Physics· Section D : M.C. PD-EM2-M/21 DSE Physics • Section D : M.C. PD-EM2-M/22 EM2 : Electric Circuits EM2 : Electric Circuits 73- < BKCE 2001 Paper II - 30 > 77. <HKCE 2003 Paper II- 33 > V +-----{ V }------. A A, s xL.-{=::J--...,---__jy .�------+I Figure(a) Figure (b) In the above circuit, the two resistors are identical. If switch Sis closed, which ofthe folloWlllgpredictions is incorrect? A. The :reading ofthe ammeterA 1 increases. Figure (a) shows a circuit used to investigate how the voltage Vacross a resistance wire varies with the current I through the B. The reading ofthe ammeter Az remains unchan ged. wire. The result is shown in Figure (b). If the experiment is repeated usin g a thinner wire of the same material and of equal C. The voltage betweenpointsXand Yin.creases. length, which of the following graphs (denoted by the dashed line) represents the expected result ? D. The power delivered by the ba ttery increases. A. B. C � 74. < BKCE 2001 Paper II- 29 > Ifthe ammeter in the circuit reads 3 A, find the voltage of the battery. A. 11 V B. 12V C. 13.SV D. 15V rn A ,�,,�'�'�' � 7S. <BKCE2002Paperll-33> 78. <BKCE 2003 PaperII-32 > V A square loop P Q R S is made of uniform resistance wire. Let X, Y andZ be the equivalent resistance of the loop when y connected as shown below: X Method of connection Equivalent resistance «:.---------+I RegionQ b:' S R X :q The figure above shows the voltage-current ( V -1) graphs of two resistors X and Y. Which of the following deductions is/are correct? (1) The resistance ofXis higher than that ofY. (2) IfXand Y are connected in series, the V-I graph of the combined resistor will lie inregionP. (3) IfX and fare connected in parallel, the V-1 graph of the combined resistor will lie in region Q. y A. (2) only S R B. (3) only C. (1) & (2) only '· D. {I) & (3) only DQ 76-. �_HKCE 2002 Paper II -30 > z In the circuit shown, both ammeters At and Ai read 1 A when the switch Sis open. Find the readings of the two R ammeters when S is closed. , A, A, A. 0.5 A I.SA Which ofthe following relatians is correct? B. 0.67A lA A. X=Y=Z C. lA 1.SA B. X=Z>Y C. X=Z<Y D. lA 3A D. X< Y<Z I DSE Physics - Section D : MC. EM2 : Electric Circuits PD-EM2-M/23 11 I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/24 11 �---; �-1 79. <HKCE2004Paperil-31> 83. <HKCE2005Paperll-19> 12V o----� 6 Vbattery s �--IV In the above circuit, what is the reading of the voltmeter when switch S is closed? A. zero B. 6V C. 12V An ammeter and a rheostat of range 0-40 n are connected to a 6 V battery. The sliding contact is located at apositionX D. It cannot be detemined since insufficient information is given. where AX "" ¼ AB as shown above. Find the ammeter reading. A. 0.ISA Questions 84 and 85 : B. 0.2A C. 0.45A D. 0.6A then:nistor 80. < HK.CE 2004 Paper II- 28 > The photograph shows a rechargeable cell If the cell is charged for 16 hours using the standard charge mode, estimate the total amount of charge flowed through the charging circuit A teacher sets up the circuit as shown in the above Figure and provides the following information to her �ts. A. 182.4C B. 3040 C Standard charge 16hours at 190mA Thermistors are devices whose resistance varies with temperature. The variation of C. 10 944C Fast charge 5 hours at 475 mA the resistance of the thermistor used with temperature is shown in the figme below. D. 27 360 C Resistance / .Q 81. < HK.CE 2004Paper II - 29 > ----s•-l----� An ammeter with negligl.Ole resistance and a high-remtance voltmeter 6V are connected into a circuit as shown. Find the mnneter and voltmeter readings. Am.meter reading / A Voltmeter reading / V 20 A 0 2 ' B. I 2 84. < HKCE 2005 Paper II - 40 > C. 3 2 Which of the following shows the variation of the ammeter reading I with the temperature ofthe thermistor{)? D. 3 w 82. < HKCE 2084 Paper II - 32> 6V 12V c::J 85. '.t=.. <BKCE2005Paperil-41> . .L. Cb. .. -�· t=. L==.. �- �- Which of the following shows the variation of the voltmeter reading Vwith the temperature of the thermistor fJ? A B. Q � In the above circuits,X, Yand Z are identical resistors. The power dissipated in Xis 20 W. Find the total power dissipated in YandZ. A. lOW B. 20W C. SOW D. 160 W I 86. DSE Physics - Section D : M.C. EM2 : Electric Circuits < BKCE 2005 Paper II • 18 > PD -EM2-M/ 2511 I 89. DSE Physics - Section D : MC. EM2 : Electric Circuits < HKCE 2006 Paper II- 23 > PD-EM2-M/2611 -----/-/"\+----/ A A, L......Cx ,__ �-\ Ifthe current in the circuit shown is 0.8 A, what is the number ofelectrons passing through the pointX in l minute? A. 8.3 X 1016 B. 1.6 x 1017 ill the above circuit, the bulbs are identical. If ht e reading ofammeter A1 is 1A. find the readings ofammeters A:zandAl, C. 5.0 X 1018 Reading of.Al Reading of.43 D. 3.0 X 102° A. 0.5A lA B. 0.5A LSA 90. < BKCE 2006 Paper II- 24 > C. 2A 2A D. 2A 3A !·-·---·-·---·-·-·-·-·-·-·-·-·-· ; 87. < HK.CE 2005 Paper IT· 39 > p I + ! 1.SV - i 1.SV ; 1.SV - ' ' ! )1.SV-- ' . '-·-·-·-----·-----·-·-·-·-·-·-· ' i.-•-•-·-•••-•-•-•-•-•-•-·-•• I battery box The diagram shows the circuit of a camping light which uses four 1.5 V cells and four identical light bulbs. The current passing through each light bulb is I A. What is the cun'ent passing through the point P and what is the power of each light bulb? Current passing through the pointP Power of each bulb A. 4A 6W B. 4A !SW A student wants o t measure theresistance ofaresistor Rand sets up a circuit as shown above. Which of the following C. IA 6W descnDe(s) themistake(s) made by the student in setting up the circuit? D. lA l.SW {1) The polarity of the ammeter is reversed. (2) The polarity of the voltmeter is reversed. (3) The voltmeter is connected across both R and the rheostat. 91. < HKCE 2006 Paper II- 26 > A. (1) only B. (2) only c. (1) & (3) only D. (2) & (3) only 88. <HK.CE 2006 Paperll-35 > ----- -----� ,.- - Lithium cell : 3.6V Capacity: 800mAh Time (stand-bymode): about3 days Three identicallight bulbs are connected to a cell as shown in the diagram. After some time, the filament of bulb Z breaks. The figure shows a ab l el on a lithimn cell of a mobile phone. The capacity 800 mA h :indicates the quantity of electric What will haPPen to the brightness ofthe remirining light bulbs ? charges that 1he cell will discharge in 3 days when the mobile phone is in stand-by mode. Estimatethe averagepower of the """""' Brightness ofX Brightness of Y cell assumlllg the vota l ge remains constant during the discharge. A. 16mW A increases B. 40mW B. increases decreases C. 120mW C. decreases increases D. 960mW D. decreases decreases 92. DSE Physics - Section D : MC. EM2 : Electric Circuits < HKCE 2007 Paper II - 20 > "' 2Q PD-EM2-M/27 1 1 96. DSE Physics - Section D : M.C. EM2 : Electric Circuits < BK.CE 2007 Paper II- 41 > PD-EM2-M/28 11 battery X y 6Q 4Q In the circuit shov;n, a voltage of 10 Vis applied acrossXY. What is the current passing through the 8 Q resistor? amm- A. 0.5 A B. 0.8 A voltmeter C. IA D. 2A 93. < HKCE 2007 Paper n - 21 > B A student sets up the above clrcuit to study the effect of the length of a resistance wire on its resistance. As the crocodile lQ clip is moved fromA to B along the resistance wire, which of the following statements is/are correct? 2'l (1) The readlllg of the ammeter lllcreases. A (2) The reading ofthe voltmeter lllcreases. sn (3) The voltmeter reading: is directly proportional to the reading of the ammeter. �- A. (l)only If the ammeter in the above circuit reads 3 A, what is the voltage of the battery? B. (2) only A. 8.SV C. (1) & (3) only D. (2) & (3) only B. 9.6V C. 21 V 97. < HK.CE 2008 Paper II- 20 > �:-�1, D. 24V The figure shows two light bulbs A andB, which are connected iD series. The voltages across A and B are 3 Vand l V respectively. Which of the 94. < HK.CE 2007 Paper 11 - 22 > following statements is/are correct ? (1) The resistance of A is greater than that ofB. The voltage and the capacity o�Jhe-ce� of a portable music player are 3.6 V and 70_0 mA h respectively. The continuous , (2) The current £lowing through A is greater than that through B. playing time of the player is 1"5 hours./The capacity 700 mA h indicates the quantity of electric charges that the cell will (3) AisdimmerthanB. discharge in 15 hours ofplayirig;• Assume that the voltage remains constant during discharge, what is the estimated power of A. (1) only the player when it is playing? B. (3) only � A 0.047W C. (1) & (2) only B. 0.168W D. (2) & (3) only C. 0.194 W 98. < HKCE 2008 Paper Il - 23 > D. 0..252W A cell fully discharges at a constant ljUITCD.t225 mA in 10 hours. If its average voltage is 1.2 V, what is the estimated total energy stored in the cell ? 95. < HKCE 2007 Paper II- 23 > A. 2.71 B. 67501 In the following circuit, three identical light bulbs are connected to a cell. Under what conditions will light bulb P have the C. 8100 J maximum brightness? D. 91201 99. < HK.CE 2008 Paper II- 21 > 6'2 12'2 A.}-c:'.=f-i 6Q SwitchX Switch Y In the above circuit, the reading of the ammeter is 0.3 A. What is the voltage Vofthe battery? A. open closed A. 4.8V B. open open B. 5.4V C. closed closed C. 9.0V D. closed open D. 14.4 V I DSE Physics - Section D : M.C. EM2 : Electric Circuits 100. < HKCE 2008 Paper Il-18 > PD-EM2- M/29 II 1 DSE Physics - Section D : M.C. EM2 : Electric Circuits 103. < HKCE 2010 Paper II- 18 > 1.SV PD-EM2-M/30 I --0-- Method of connection Equivalent resistance X y- y In the circuit above, voltmeters P and Q of very high resistance are connected across the switch and the light bulb respectively. What are the voltm.eter readings when the switch is open ? A. reading of P JV 0 reading of Q/V 0 --y B. 0 1.5 C. l .5 0 z D. LS 1.5 "'* '-l-----+------§' 104. < HKCE 2010 Paper II- 21 > x A circular loop is made of uniform resistance wire. Let X. Y and Z be the equivalent resistance of the loop when connected ___,_a p R cp, as shown above. Which of the following is correct ? A. X= Y=Z B. X> Y=Z C. X<Y=Z D. X<Y<Z 101. <BKCE 2009 Paperll-19 > Q s Three identical bulbs x;YandZ ate connected to a 12 V battery in the circuit above. Which of the following statements are �-- •--1--� Two identical resistors are connected in series in the circuit shown. 12V correct? What are the readings of the voltmeter when S is open and when S is closed respectively 7 (1) The voltage across PQ is greater than 6 V. (2) The voltage across QS is zero. Sis open Sis closed s (3) If Ybums out and becomes open circuit, Zbecomes brighter. ""' A. (1) & (2) only A. B. C. =• 12V 6V 12V 6V '-------{v B. (1) & (3) only C. (2) & (3) only D. 12V 12V D. (!), (2) & (3) 102. <IIKCE 2010 Paperll-17> 105. < HKCE 2010 Paper II- 41 > s A car bas two doors and an indicator lamp is installed to act as j\ car door watlling signal. When either or both doors are "' E� open, the lamp lights up. A student designs four different circuits for this application. A switch is installed in each door. The switch is open when the car door opens. Which ofthe following circuits is correct ? A. R R 1n Q A c. D. � In the circuit shown, wires Xand Yare to be connected to two points in the resistor networkPQRS. Across which two points should.X and Ybe connected to so that tbeammtu:r reading will be a .minimum ? A. Pand.Q B. QandR C. RandS D. SandP I DSE Physics - Section D : MC. EM2 : Electric Circuits PD -EM2-M/31 I I DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-EM2-M/32 II 106.. < HKCE 2011 Paper Il - 18> Part B : HKAL examination questions The figure below shows the current-voltage (l-V) graphs oftwo resistors P and Q. I 110. < HK.AL 1980 Paper I- 21 > p The voltmeter reads 3 V in the circuit shown. The e.m.f. of the battery is 15 V. If the internal resistance of the battery is negligible. What is the internal resistance of the voltmeter ? Q 3kn ,1,_____ A 0.75kn lk.G B. I.SO kn C. 3.00kn '--------i D. 3.75kn lSV Which ofthe following statements about the two resistors are correct ? (1) Both ofthem obey Ohm's law. (2) The resistance of Pis greater than that of Q. 111. <BKAL1980Paperl-47> (3) If they are connected in parallel to a battery, the current passing through P will be greater than that passing throughQ. When the switch Sis closed in the circuit shown, only L1 lights up. A. (1) & (2) only Which ofthe following possibilities would account for this ? B. (1)&(3)only (1) There is a short circuit across 4 C (2) & (3) only (2) The :filament ofLz is burnt out. D. (1), (2) & (3) (3) The :filaments ofbothl,z and[,,. are burnt out. 2V I ?. A (1) only 107. < HKCE 2011 Paper Il- 19 > B. (3) only C. (1) & (2) only Which of the following resistor networks gives the largest equivalent resistance across PQ if all the resistors have the same D. (2) & (3) only resistance? A. B. 112. < HKAL 1982 Paper I- 22 > In the circuit shown, an electron travelling from Yto X through R1 loses energy E1, and an electron travel.ling from Yto Xtbrough R2 loses energy E2. What is the relation betweenE1 andE2? c. D. A. 4E1 = Bi xr-----,==i----➔r B. 3E1 = E2 & = 30 C. E1 = Bi p Q D. Ei = 3E2 113. <HKAL1983PaperI-20> In the circuit shown, X and Yare two identical cells, of e.m.f. 10 V and 108. < HKCE 2011 Paper n - 20 > 6Q internal resistance 4 n. What is the current given out by each cell? A. zoro Jn the circuit shown, the ammeter reading is LOA when Sis open. X SQ y What is the ammeter readingwhenS is closed? B. 0.42A A A. I.SA C. 050A 60 B. 2.0A D. 0.83 A C. 2.5 A 3!l s D. 3.0A 114. < HK.AL 1984 Paper I- 21 > 109. < HKCE 2011 Paper Il- 40 > An ideal voltmeter is connected between points X and Yin the circuit 12V 3!l shown. Find the readings of the voltmeter when the switch is open and In the circuit shown, both bulbsXand Yligb� up normally. Both the closed respectively. ammeter reading and the voltmeter reading are non-zero. Which of the following will cause theammeter reading to drop to zero while X y A switch open switch closed the.:voltmeterreading is stillno'i-zero? Assume meteria!'e ideal. A. l.SV 25V y A. Bulb Xbecomes short circuit. B. 2.SV 8.0V B. Bulb Ybecomes short circuit. C. BulbXis burnt out and becomes open circuit. C. 12V 4.SV '-----/ V }-----_J D Bulb Yis burnt out and becomes open circuit. D. 12V 75V 11 115. <HKAL 1985 PaperI-44 > DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-E M2-M/3 311 I 119. <HKAL1989P.aperI-28> DSE Physics - Section D : M.C. EM2 : Electric Circuits PD- EM 2-M / 3411 , �;�7 The e.m.f. of a battery is equal to (1) the electrical power it given out divided by the cunentit delivers. (2) the elecirical energy it transfers to unit coulomb of charge passing through the battery. CL---�� (3) its terminal voltage when the battery is on open circuit. A. (3) only B. (1) & (2) only C. (2) & (3) only In the circuit shown, Vis a voltmeter nfbjgh intemal resistanc'I and A is an ammeter oflow internal resistance. What is the D. (1), (2) & (3) voltmeterreading when (a) switchK is open, (b) switchK is closed? Kopcn K closed 116. <RKAL 1986 Paperl-34 > "' sn ,n A. B. C. av av 3V OV 2V 2V D. 3V av A "' X y "' B 3n 120, < HKAL 1989 Paper I- 29 > "' In the circuit shown, four resistors are connected to form a network. "' "' The equivalent resistance between A andB is A. o.s n. sn�sn A�t In the circuit shown, if a battery of e.m.f. 20 V with neglig1Dle internal resistance is connected across XY, what is the current B. 120. given out by this battery ? c. un. A. 1.0A. o. 2.on. B. 2.0A. 40 c. 2.5 A. D. 4.0A 121. <HKAL 1990 PaperI-33 > In the circuit shown, the battery has negligible internal resistance. The cuttentl delivered by the battery is 117. < BKAL 1987 Paper I - 31 > A. 0.5 A. B. 0.9 A. A"--'r---..-c=:H s B sn C. 1.2A. D. 1.5 A. ·,.L ·,.� ",t= · . b 2V 122.. < BKAL 1990 Paper I- 34 > In the above figure, AB is a resistance wire of uniform cross--section. and S is a sliding contact The 2 V battezy has' negligr.ble intemal resistance, and the connected voltmeter is ideal 'Which of the fullow:ing graphs shows the correct Which ofthe following circuits is best used for the measurement of a high resistance R? variation of voltage mea51Il"ed by the voltmeter when the contacts is moved from A to B? A - � + R A - A B A B A B A B 118. <HKAL 1989 Paper I- 31 > C. D. In the circuit shown. AB is a metre-wire ofresistance 12 n. V&en Xis moved � to the mid-point ofAB, the p.d. across AX will be R + R A. 0.9V. A - B. 1.2V. C. UV. D. 1.8 V. I DSE Physics - Section D : M.C. EM2 : Electric Circuits 123. < HKAL 1995 Paper 11A - 23 > PD-E M2-M /35 11 Ii 127. <HKAL1999PaperIIA -17> DSE Physics - Section D : M.C. EM2 : Electric Circuits PD-E 2�1 M Two cells of negligible internal resistance are connected with two resistors Three resistors of resistanceRi,Ri andR; are connected in parallel. It is known thatR1 > R2 >RJ. The equivalent resistance as shov..n. What is the potential difference between% and Y? of this combination isR. Which of the following statements is/are correct? A. 1.33 V (1) Energy dissipated in moving l C ofcharge through the resistor ofresistanceR1 is greater than that throughR2. (2) RissmallertbanR1. B. 1.67V (3) Ifthe resistor with resistanceR; is removed, the resulting equivalent resistance is increased. C. 2.00V A. (I) only D. 233V B. (3)only C. (!) & (2) only D. (2) & (3) only 124. < HKAL 1997Paper IIA- 25 > Two cylindrical wires, Xand Y, are made from the same metal and have the same volume. The length ofXis three times that �----1 128. < BKAL 1999Paper IIA - 19 > of Y. If currents of 1 A and2 A pass tbroughXand Yrespectively, the ratio of the power dissipation inXto that in Yis A. 1: 4 In the circuit shown, the battery has negligible internal resistance. B. 9 :2 The three resistors have same resistance. If switch S is closed, what C. 3:4 would happen to the electric potential at pointsX and at Y? D. 9:4 Potential at X Potential at Y R, A. increase in,,,.,, X R, y 125. < HKAL 1998Paper llA - 19 > B. increase decrease ,n.,,.,,, R, ,j s = current/ A C. decrease D. decrease doo,ease 5.0 ------------------- 129. < RKAL 1999Paper IIA- 16 > 1.0 '-====---'------'-----� ,._.___......, V ,._______, o voltage/ V 10 20 The variation of current with the voltage applied across a device is as shown in the figure. 'What is the change in resistance R of the device when the voltage in.creases from IO Vto 20 V? The above circuit can be used to find the r esistance of the resistor R. The voltmeter and the ammeter are not ideal. Which of A. It increases by 2.5 .n. the following statements is/are correct? B. It decreases by 15 .0.. (I) The reading of the ammeter is in fact larger than the actual current passing throughR, c. It increases by 6 n. (2) The ratio ofvoltm.eterreading to ammeter reading is in fact smaller than the resistance ofR. D. It decreases by 6 .Q_ (3) The circuit is suitable fur measuring high resistance. A. (!) only '11, (3) only 126. <HKAL1998PaperlIA-39> --.....,11 ......-- C. (!) & (2) only TJ. (2) & (3) only 130. < HKAL 2000Paper IlA - 23 > s In the above circuit, the two resistors are identical. The battery has an e.m.£ of 4V and it has negligible intemaJ. resistance. The voltmeter is ideal. What are the voltmeter readings 'Ml.en Sis open and when Sis closed ? 1Q R The figure shows part of the circuit in a network of resistors. According to the matl<:.ed values, find the magnitude and Sopen Sclosed direction ofthe current passing through the resistorR. A. 2V 4V A. 0.2 A from right to left B. 2V 2V B. 0.2 A from left to right C. ov 4V C. 0.4 A from right to left D. 4V ov D. 0.4 A from left to right I DSE Physics - Section D : M.C. EM2 : Electric Circuits 131. < HKAL 2003 Paper IlA - 25 > 6V PD-E M2-M 3 / 7 11 DSE Physics - Section D : M.C. EM2 : Electric Circuits 135. < HKAL 2008 Paper 11A - 15> PD-EMZ-M/ 81 3 In the circuit shoVlll, a battery of e.m.f. 6 V and negligible internal resistance is connected to three resistors. What are the electric potential at Xbefore and after switch S is closecj. ? �-----a1111---� current JI mA ' 100 0 Before After 0 ./ A, +6V +3V 1./ I/ 40 B. +3V +3V s 0 C. +2V +2V / D. +2v +3V voltage V/V 4 The above graph shows theJ-Vrelationship of an electric device. V/bich ofthe following statements is/are correct? 132. < HKAL 2003 Paper IIA- 27 > 20 (1) When the applied voltage is 0.5 V, the resistance of the device is mfuilie. In the circuit shown, the battery bas constant e.m.f. and negligible in� resistance. An ideal voltmeter connected ,----C:=f---r---C:=}---x (2) When the applied voltage is between 1 V and 5 V, the resistance ofthe device is constant. (3) -when the applied voltage is between 1 V and 5V, the current is directly proportional to the voltage. across terminals Xand Yreads 2 V. Ifan ideal ammeter is A. (1) only connected across X and Y, the ammeter should read B. (3) only '--c=:::i-----c=:::i- "' - 2" A. 0.3A C. (1) & (2) only B. 0.5A D. (2) & (3) only C. 0.6A 20 D. LOA y 136. < HKAL 2009Paper IlA- 28 > p 133. < BKAL 2003 Paper IIA- 20 > R X B=---C:=J--�C p R 9V-=- 100 R V y A'----C:=J----">oD Q '-----Q In the network of resistors shown above, the resistance of Sis infinitely large and the two resistors R are identical. If the Figure(a) Figure (b) equivalent resistance across CD is 25 n, what is the equivalent resistance across AC? Figure (a) shows a rotary-type potential divider PQR connected to an 9 V battery of negligible internal resistance. The A. 250 internal structure of the potential divider is shown in Figure (b). XYZ is a uniform resistance wire in the form of a circuit arc B. 35.0 with centre O and LXOY= 90°. OZ is a sliding contact and LXOZ= 120°. Find the reading of the ideal voltmeter. c. son A. 2.5 V D. infinitely large B. 4.0V C. 5.0V D. 6.8V 134. <IIKAL 2007 PaperllA- 16> voltage VIV 137, <.HKAL 2010 PaperJIA- 23 > In the network shown, the resistance ofeach resistor is 6 n. 4 Find the equivalent resistance·ofthe network across a and b. I 2 0 ' A. 1.20 B. 1.5n C. 2.00 ;/ Y, D. 2.4Q 6 4 ' 2 138. <HKAL2010PaperllA-25> � current!/ A 0.2 Which of the following statements concerning an ammeter are correct ? 0.4 0.6 The above figure shows the V-1 characteristic curves ofresistance wire X and filament bulb Y. If they are connected in series t0 An ammeter should be connected in series to a circuit. R,] An ammeter should·have a low resistance. to a 12 V d.c. supply ofnegligible internal resistance, what is the voltage across the resistance wireX? (3) An ammeter ofhigh resistance significantly changes the current in the circuit to which it is connected. A- 9V A. (1) & (2 ) only B. 8V B. (1) & (3) only C. 7V C. (2) & (3) only D. 6V D. (1), (2) & (3)