SYLLABUS FOR SESSION 2021 - 22 Term - I I UNIT TERM - I I MARKS I 1 - Carbon and its Compound 2 - Periodic classification of Elements 10 II 1 - How do organism Reproduce 2 - Heredity and Evolution 3 - Our Environment 16 III 1 - Electricity 2 - Magnetic effect of current 14 TOTAL 40 CHAPTER - ELECTRICITY SECTION - A (2 MARKS) 1. How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line? 2. Given n resistors each of resistance R. How will you combine them to get the maximum and minimum effective resistance? What is the ratio of the maximum to minimum resistance? 3. Two electric bulbs A and B are marked 220 V, 40 W, and 220 V, 60 W respectively. Which one of the two has greater resistance? 4. Two students perform the experiments on series and parallel combinations of two given resistors R l and R 2 and plot the following V - I graphs. Which of the graphs is (are) correctly labelled in terms of the words ‘series’ and parallel’ Justify your answer? 5. Should the heatin g element of an electric iron be made of iron, silver or nichrome wire? Justify giving three reasons? 6. An electric motor takes 5 A from a 220 V line. Determine the power of the motor and energy consumed in 2 h. 7. Two wires of equal cross sectional area, one of copper and other of manganin have same resistance. Which one will be longer? 8. Two cubes A and B are of the same material. The side of B is thrice as that of A. Find the ratio R A /R B 9.Find the net resis tance between A and B in the following network 10. What is the equivalent resistance between A to B in the network shown in the figure. Series Paralle l Parallel Series V I I V 11. Mention two differences between a voltmeter and an ammeter. 12. What is the commercial unit of electric energy? Convert it into joules 13. Current I flowing through a resistorresults in dissipation of power P. By what percentage will the power dissipated in the res istor increase if current through the resistor is increased by 50%. 14. A wire of resistance 5 ohms is bent in form of a closed circle. What is the effective resistance between the two points at ends of any diameter of the circle? 15. Draw a schematic di agram of an electric circuit comprising of 3 cells and an electric bulb, ammeter, plug - key in the ON mode and another with same components but with two bulbs in parallel and a voltmeter across the combination. 16. Consider the following circuit diagram. If R 1 = R 2 =R 3 = R 4 = R 5 = 3 Ω, find the equivalent resistance (R s ) of the circuit. 17. In an experiment to study the relation between the potential difference across a resistor and the current through it, a student recorded the following observations: - On examining the above observations, the teacher asked the student to reject one set of readings as the values were out of agreement with the rest. Which one of the above sets ofreadings can be rejected? Calculate the mean value of resistance of the resist or based on the remaining four sets of readings. 18. Explain the role of fuse in series with any electrical appliance in an electric circuit. Why should a fuse with defined rating for an electric circuit not be replaced by one with a larger rating? 19. Find the current drawn from the battery by the network of four resistors s hown in the figure. 20. Write two points of difference between electric energy and electric power Potential difference (V) 1.0 2.2 3.0 4.0 6.4 Current (A) 0.1 0.2 0.6 0.4 0.6 SECTION - B(3 MARKS) 1. For the circuit shown in this diagram, calculate (i) the total resistance of the circuit (ii) the total current flowing through the circuit (iii) the potential difference across 10 Ω resistor 2. Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V? 3. Show how you would connect three resistors, each of resistance 6 Ω so that the combination has resistance of (i) 9Ω (ii) 4Ω. 4. Two resistors of 2 Ω and 4 Ω are in turn connected (i) in series, (ii) in parallel to a given source for the same time interval. Compute the ratio of total hea t produced in the combination in two cases. 5. An electric iron consumes energy at a rate of 840 W when heating is at the maximum rate and 360 W when the heating is at the minimum. The voltage is 220 V. What are the current and the resistance in each case ? 6. In the circuit given below, if the current reading in the ammeter A is 2A, what would be the value of R 1 ? 7. (a) What is meant by ‘Electric Resistance’ of a conductor? (b) A wire of length ‘ L ’ and resistance ‘ R ’ is stretched so that its length is doubled and the area of cross section is halved. How would its (i) resistance change (ii) resistivity change? 8. (a) State O hm’s law? ( b ) The values of current ‘ I ’ flowing in a given resistor for the corresponding values of potential difference ‘ V ’ across the resistor are given below: I (amperes) 0.5 1.0 2.0 3.0 4.0 V (volts) 1.6 3.4 6.7 10.2 13.2 Plot a graph between V and I and also calculate resistance. 9. For the parallel combination of resistors establish the relation: 1/R = 1/R 1 + 1/R 2 + 1/R 3 Where the symbols have their usual meanings. 10. For the series combination of resistors establish the relation: R = R 1 + R 2 + R 3 Where th e symbols have their usual meanings. 11. Ohm’s law experiment is performed separately with individual resistor R 1 , R 2 [R 1 > R 2 ] and series combination of R 1 , R 2 . Graph is plotted between potential difference (V) and current (I) as shown in figure for each case: Identify which one is for R 1 , R 2 and combination of resistors. (Justify your answer for each case). 12. The current flowing through a resistor connected in an electrical circuit and the potential difference developed across its ends are shown in the given ammeter and voltmeter. (i) Find the least count of the voltmeter and ammeter. (ii) What is the voltage and the current across the given resistor? (iii) Calculate the resistance of the resistor. 13. Find out the following with reference to the circuit diagram given below: (a) Current through 4Ω resistor. (b) Current through each 8Ω resistor. (c) potential difference across each resistor 14. Explain the following: (a) Why is the tungsten used almost exclusively for filament of electric lamps? ( b ) Why is the series arrangement not used for domestic circuits? ( c ) Why are copper and aluminium wires usually employed for electric transmission? 15. Two identical resistors each of resistance 12 Ω are connec ted (i) in series (ii) in parallel, in turn to a battery of 6 V. Calculate the ratio of power consumed in the combination of resistors in both cases. 16. (a) Which has more resistance: 100W bulb or 60W bulb? (b) Which of them glows more when connected to the same source in (i) series (ii) parallel? 17. Three resistors of 5 Ω, 10 Ω and 15 Ω are connected in series and the combination is connected to battery of 30V. Ammeter and voltmeter are connected in the circu it. Draw a circuit diagram to connect all the devices in proper correct order. What is the current flowing and potential difference across 10 Ω resistance ? I V A B C 18. State the law that governs the amount of heat produced in a metallic conductor when electric c urrent is passed through it for a given time. Also express this law mathematically. 19. A household uses the following electric appliances: Refrigerator of rating 400W for 10 hours each day. Two electric fans of rating 80W each for 12 hours each day. Six electric tubes of rating 18W each for 6 hours each day. Calculate the electricity bill of the household for the month of June if the cost per unit of electric energy is Rs. 3.00. 20. Two metallic wires A and B are connected in series. The wire A has length l and radius r, while wire B has length 2l and radius 2r. Find the ratio of total resistance of series combination and the resistance of wire A, if both the wires are of same material? SECTION - C : CASE - BASED QUESTIONS Case Study - 1 Read the passage and answer the following questions: - The heating effect of current is obtained by transformation of electrical energy into heat energy. Just as mechanical energy used to overcome friction and is converted into heat, in the same way, electrical energy is c onverted into heat energy when an electric current flows through a resistance wire. The heat produced in a conductor when current flows through it is directly proportional to the square of current, resistance of wire and time for which current is passed. T he mathematical expression is given by H= I 2 Rt 1. Find the heat produced in a wire of resistance ‘a’ when a current ‘b’ flows through it in time ‘c’? 2. What are the properties of a heating element? 3. Calculate the heat produced when 96,000 coulombs of charge are transferred in one hour through a potential difference of 50 volts? Or Find the heat energy produced in a resistance of 10 Ω when 5 A current flows through it for 5 minutes. Case Study - 2 Read the passage and answer the following questions: The relationship between potential difference and current was first established by George Simon Ohm. This relationship is known as Ohm’s law. According to this law, the current passed through a conductor is proportional to the potential difference applied betw een its ends provided the temperature remains constant i.e. I α V or V=IR where R is the constant for the conductor and it is known as resistance of the conductor. Although Ohm’s law has been found valid over a large class of materials, there are some mate rials which do not hold Ohm’s law. 1. What is the nature of V - I graph ? 2. When a battery of 9V is connected across a conductor and the current of 0.1 A flows through it, find the resistance? 3. If both the potential difference and the resistance in a circu it are doubled, then what will happen to the current? Or A resistance wire of 25 ohm is cut into five equal parts and all are connected in parallel. What will be the equivalent resistance of the combination? Case Study - 3 Read the passage and answer the following questions: - The obstruction offered by a conductor in the path of a flow of electrons is called resistance. The SI unit of resistance is Ohm. It has been found that the resistance of a conductor depends on the te mperature of the conductor. As the temperature increases, the resistance also increases. But the resistance of alloys like manganin and constantan is almost unaffected by the temperature. The resistance of a conductor also depends on the length of the cond uctor and the area of cross - section of the conductor. A long wire has more resistance than a short one. 1. If the area of cross - section of a conductor is halved, then what will be its effect on its resistance? 2. If the diameter of a wire is doubled, then what will be its effect on the resistance? 3. Calculate the area of cross section of a wire of length 1.0m, its resistance is 23Ω and the resistivity of the material of the wire is 1.84×10 − 6 m OR A wire of resistance R is stretched to double its length. What will be its new resistance? Case Study - 4 Substances through which charges cannot pass are called insulators. Glass, pure water and all gases are insulators. Insulators are also called dielectrics. In insulators, the electrons are strongly bound to their atoms and cannot get themselves freed. Thus, free electrons are absent in insulators. Insulators can easily be charged by friction. This is due to the reason that when an electric charge is given to an insulator, it is unable to move freely and remai ns localized. 1. Calculate the current in a wire if 1500 C charge is passed through it in 5 minutes? 2. A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Find the amount of electric charge that flows through the circuit? 3. Which one is having lesser resistance : A 60 W bulb or a 40 W bulb ? Or Ten identical bulbs are connected in a series circuit to a power supply line and the same ten identical bulbs are also connected in a parallel circuit to an identical power supply line (a) Which circuit would have the highest voltage across each bulb? (b) In which circuit would the bulb be brighter? Case Study - 5 Two students while performing an experiment on ohm’s law have recorded their observations in a table and to verify the same they are given with a standard measurement table (Table - 1). The values of experiment are recorded by the two students in Table - 2 . Table - 1 (Standard Measurement) Sl. No. Volt meter reading(mV) Ammeter reading (mA) 1 2 0.5 2 4 1 3 6 1.5 4 8 2 5 10 2.5 Table - 2 (Measurement by students) (a) What is the value of resistance calculated from the standard measurement? (b) Which set of reading recorded by Student - Y is correct? (c) While performing this experiment both the students have kept which physical quantity constant? If the same physical quantity increases, then the resistance of a general resistor wi ll _____________. OR After conducting the experiment both the students have concluded that the current and Potential difference is directly ________________. W hat will happen to the current when the resistance in a circuit increases with constant voltage? Student Sl. No. Volt meter reading(mV) Ammeter reading (mA) Student - X 1 4 1 2 6 2 3 8 2 Student - Y 1 6 1 2 8 2 3 10 3 ANSWERS CHAPTER - ELECTRICITY SECTION - A(2 MARKS QUESTIONS) 1. Let n resistor s of 176 Ω are joined in parallel. Their combined resistance (R) , 1/R = 1/176 + 1/176 ...... times = n/176 or R = 176/n Ω R = V/I = 220/5 = 44 Ω 176/n = 44 Ω n = 176/44 = 4 2. F or maximum resistance Rs=nr (Equivalent of series combination) F or minimum resistance Rp= r/n (Equivalent of parallel combination) Rs/Rp= n 2 3. P = V 2 / R R α 1/P if V = constant Therefore, bulb A (40 W) has greater resistance than the bulb B. 4. Both are correct because ∆V/∆I= resistance(R) and ∆ I/ ∆ V=1/R Series means high resistance and parallel means low resistance. 5. Heating element of an electric iron is made up of nichrome wire because of thefollowing reasons. a. Resistivity is high because of which more heat is produced due to the passage of current. b. Melting point is high. c. It does not oxidize (or burn) easily at high temperature. 6. P = VI = 220 x 5 = 1100 W E = p x t =1100 W x 2 h = 2200 Wh = 2.2 KWh 7. R = ρL/A ρL = constant (R,A=const) ρ α 1/L ρ ( manganin ) > ρ ( copper ) L ( copper ) > L ( manganin ) 8. R A = ρL/A R B = ρ3L/9A R A : R B = 3:1 9. For path acb , Rs = 3 + 3 = 6 Ω Resistance between A and B, R = 2 Ω 10. The equivalent circuit diagram is Hence equivalent resistance R’=R/3 11. Voltmeter . It is used to measure P.D. across two points in an electric circuit. Its resistance is very high. A voltmeter is connected in parallel in an electric circuit Ammeter : It is used to measure electric current in an electric circuit. Its resistance is very low. An ammeter is connected in series in an electric circuit. 12. Kilowatt hour – Commercial unit of electrical energy 1 kWh = 1000 Wh = 1000 J/S x 3600 sec = 3600000 J = 3.6 x10 6 J 13. P=I 2 Rt I’=I+(50/100) I=3/2 I P’=I’2Rt=9/4 P Percentage increase in power = ( P’ - P ) /P x 100 = 5/4 x 100 =125% 14. R=(5/2)/2=5/4=1.25 ohm 15. 16. 17. The third reading for V= 3.0 volt and I= 0.6 A will be rejected as it has larger deviation from the rest of the readings. The value of resistance in the other four observations will be 10 ohm, 11 ohm, 10 ohm and 10.67 ohm So, the mean value of the resistance = 41.67/4=10.417=10.42 ohm 18. Fuse wire is a safety device connected in series with the live wire of circuit. It has high resistivity and low melting point. It melts when a sudden urge of large current passes through it and disconnects the entire circuit from the electrical supply. But, in case if we use a larger rating instead of a defined rating, then it will not protect the circuit as high current will easily pass through it and it will not melt. 19. 20. SECTION - B( 3 MARKS QUESTIONS ) 1. (i) 3Ω and 6Ω are in parallel 1/Rp = 1/3 + 1/6 = 1/2 Rp = 2 Ω Rp and 10 Ω are in series Rs = Rp + 10 = 2 + 10 = 12 Ω (ii) Total current = V/Rs = 12/12 = 1 A (iii) P.d across 10 Ω = 1 x 10 = 10 V 2. Current draw n by 1st lamp rated 100 W at 220 V, I 1 = P/V = 100/ 220 = 5/11 A. Current drawn by 2nd lamp rated 60 W at 220 V, I 2 = 60/220 = 3/11 A. In parallel arrangement the total current, I = I 1 +I 2 = 3/11+ 5/11 = 8/11 = 0.73 A. 3. i.To get net resistance of 9 Ω we should join three resistors as below: ii.To get 4Ω net resistance we should join three resistors as below: 4. H = I 2 Rt In series combination the heat produced Hs = V 2 /36 X6Xt = V 2 /6X t joules In parallel combination the heat produced Hp = V 2 /2 X t + V 2 /4 X t = 3/4 V 2 t Hs/Hp = (1/6)/(3/4) = 2/9 5. 𝑃 = 𝑉𝐼 and 𝐼 = 𝑃 / 𝑉 Case I: For maximum heating rate, 𝐼 =840/220 = 3.82 𝐴 𝑅 = 𝑉 / I = 220/3.82 = 57.60 Ω Case II: For minimum heating rate, 𝐼 =360/220 = 1.64 𝐴 𝑅 = 𝑉 / I = 220/1.64 = 134.15 Ω 6. 5 O hm, 10 ohm and R1 are in series 1/R p = 1/5+1/10+1/R 1 1/R p = (2+1)/10 + 1/ R 1 = 3/10 +1/ R 1 1/R p = (3 R 1 +10)/10 R 1 R p = 10 R 1 / (3 R 1 +10) Now, 6 ohm, 6 ohm and R p are in series Thus, Req = 12 + 10 R 1 / (3 R 1 +10) ------------------ (1) (1 mark) V = I Req From the circuit Req = 30/2 = 15 A --------------- (2) (1 mark) Equating (1) and (2) 12 + 10 R 1 / (3 R 1 +10) = 15 10 R 1 / (3 R 1 +10) = 3 10 R 1 = (9 R 1 + 30) Thus, R 1 = 30 ohm. (1 mark) 7. (a) It is defined as the ratio of p.d across the conductor to the current passing through the conductor. R = V/I . (b) (i) R 1 = ρ L 1 /A 1 L 2 = 2 L 1 and A 2 = A 1 /2 R 2 = ρ L 2 /A 2 = ρ 2 L 1 /A 1 /2 = 4 ρ L 1 /A 1 = 4 R 1 Resistance becomes 4 times its original resistance. (ii) Resistivity remains unchanged as it depends on nature of material not on L and A 8. (a) At constant temperature the electric current flowing in a conductor is directly proportional to the potential difference across the end of a conductor provided the temperature and other physical conditionsof the conductor remain the same. (b) Correct graph R = 3.33 Ohm 9. Correct derivation. 10. Correct d erivation. 11.I n V - I graph slope of the graph is directly proportional to the resistance (i) Slope of A is maximum which represents series combination of resistances (ii) Slope of B is more than C but less than A, so it represents R 1 (iii) Slope of C is minimum, so it represents R 2 12. (i) Least count, Ammeter=0.2/10 =0.02 A. Voltmeter= 1/10 =0.1 V (ii) Voltage V=2.1 V, Current I= 0.3 A (iii) Resistance R=V/I =2.1/0.3 =7 Ohm. 13. Total resistance R =4+(8x 8/8+8) = 8Ω. Current drawn from the cell = 8/8 =1A. (i) Current through 4Ω resistor I= 1A (ii) Current through each 8Ω resistor is 0.5 A (ii i) P otential difference across 4Ω resistor V 1 =1x 4 =4V, Potential difference across each 8Ω resistor, V 2 =V 3 = 8 - 4 =4V 14. a For filament of electric lamp we require a strong metal with high melting point. Tungsten is used exclusively for filament of electric lamps because its melting point is extremelyhigh. b Series arrangement is not used for domestic circuits as current to all appliances remain same in spite of different resistance and every appliance can not be switched on/ off independently. c Copper and aluminium wires are usually employed for electricity transmission because they are good conductor with low resistivity. They are ductile also to be drawn into thin wires. 15. Case i: Total resistance R =12+12 =24Ω, So P 1 =V 2 /R = 6X6/24 =3/2 W Case ii: Total resistance R =12X12/12+12 =6Ω, So P 2 =V 2 /R = 6X6/6 =6 W Hence, P 1 /P 2 =1:4 Alternate way: As V is constant in both cases, So P α 1/R, Hence , P 1 /P 2 = R 2 /R 1 So, P 1 /P 2 =6/24 =1:4 16. (a) R = V 2 /P As R is inversely proportional to P for constant V. Thus, the resistance of 60W bulb is more. (b) (i) In parallel 100W bulb glows more, because H== V 2 t/R resistance is less hence glows more. (ii) In series 60W bulb glows more, because H=I 2 Rt and same current flows through both the bulb, hence 60 W b ulb glows more. 17. Circuit diagram (To be drawn) Total resistance R=5+10+15 =30Ω , Current drawn I= V/R =30/30 =1A As they all are in series current remains same across all the resistors i.e 1A So potential difference across 10 Ohm resistance V 1 =IR 1 =1 x 10 =10 V 18. Statement of the Joule’s law Mathematical expression H = I 2 Rt 19. Electrical energy consumed per day =400 x 10+2 x 80 x 12+6 x 18 x 6 =4000+1920+648 = 6568 Wh = 6.568 kWh Electrical energy consumed in 30 days= 6.568 x 30 = 197.04 kWh (units) Electric Bill = 197.04 x 3 = Rs 591.12. 20. R A = ρ L/A = ρ L/ π r 2 R B = ρ 2L/ π (2r) 2 = ρ 2L/4 π r 2 R = R A + R B = 3 ρ l/2πr 2 R/R A = 3/2 SECTION - C : (CASE - BASED QUESTIONS ) Case Study - 1 1. ab 2 c 2. high melting point and high resistance 3. H = V Q = 50 X 96000 = 4800000J = 4800 KJ Or R = 10 Ω, I = 5 A, t = 5 minutes = 5 × 60 s H = I 2 R t = 5 2 × 10 × 5 × 60 =25 × 10 × 300 =25 × 3000 =75000 J (or) 75 kJ Case Study - 2 1. Straight line 2. R = V/I = 90Ω 3. Current remains the same I = V/R I’ = 2V/2R = I O R Each part has resistance 5 Ohm. Net R =1 Ohm I = V/R I’ = V/2R = I/2 Case Study - 3 1.It will become 2 times 2.It will become one - fourth 3. R=pL/A A = ρL/R = 0.08 X 10 - 6 m 2 OR R=pL/A R’ =p 2 L/A /2 = 4 R Case Study - 4 I = Q/ T = 1500/ 5 x 60= 1500/300= 5 A 2.Q=It=0.5A x 600s=300C 3. R = V 2 /P Rα1/P if V =Const Hence, bulb of higher wattage will have less resistance. In other words, resistance of 60W bulb is less than the resistance of 40 W bulb. Or (a) parallel circuit. (b) In parallel connection Case Study - 5 (a) 4 ohm (b) second observation (c) temperature, increases OR proportional, decreases CHAPTER: MAGNETIC EFFECTS OF ELECTRIC CURRENT SECTION - A (2 marks) Q1. What are magnetic field lines? Draw a diagram to represent a uniform magnetic field in a given region. Q2. (i) When does a current carrying conductor kept in a magnetic field experience maximum force? (ii) List the factors on which this force depends? Q3. Name the physical quantities which are indicated by the direction of thumb and forefinger in the Fleming’s right hand rule? Imagine you are sitting in a chamber and you observe that an alpha particle is moving vertically upwards is deflected by a strong magnetic field towards you. Wha t is the direction of magnetic field? Q4. (i) Write the conclusion made by the Oersted on the basis of his experiment with current carrying conductors. (ii) In the given figure, identify the poles P and Q. Give reason for your answer. Q5. Write one application of for each of the following: (a) Right - hand thumb rule (b) Fleming’s right hand rule OR (a) Maxwell corkscrew rule (b) Fleming’s left - hand rule Q6. How will the magnetic field produced at a point due to a current - carrying circular coil change if we: (i) increase the current flowing through the coil? (ii) reverse direction of current through the coil? OR (i) What does the pattern of field lines inside the solenoid indicate? (ii) W hat type of core is used to make an electromagnet? Q7. The given magnet is divided into three parts A, B, and C. Name the parts where the strength of the magnetic field is: (i) maximum (ii) minimum. How will the density of magnetic field lines differ at these parts? OR Name the scientist who discovered the reverse process of magnetic effects of electric current. With which name is this phenomenon known? What is the function of galvanometer in a circuit? Q8. (a) Draw a diagram to represent a uniform magnetic field in a given region. (b) List two properties of magnetic field lines. Q9. A compass needle is placed near a current - carrying wire. State your observation for the following cases, and give reason for the same in each case. (a) Magnitude of elec tric current in the wire is increased. (b) The compass needle is displaced away from the wire. Q10. Identify the poles of the magnet in the given figure (1) and (2). Q11. (a) Two magnets are lying side by side as shown below. Draw magnetic field line between poles P and Q. (b) What does the degree of closeness of magnetic field lines near the poles signify? Q12. State the rule to find the direction of magnetic field associated with a current carrying conductor. What is the shape of a current carryin g conductor whose magnetic field pattern resembles that of a bar - magnet? Q13. The magnetic field associated with a current - carrying straight conductor is in anticlockwise direction. If the conductor was held along the east - west direction, what will be the direction of current through it? Name and state the rule applied to determine the direction of current. Q14. It is established that an electric current through a metallic conductor produces a magnetic field around it. Is there a similar magnetic field prod uced around a thin beam of moving (i) alpha particles, (ii) neutrons? Justify your answer. Q15.What is the role of the two conducting stationary brushes in a simple electric - motor? Q16. Meena draws magnetic field lines of field close to the axis of a current carrying circular loop. As she moves away from the centre of the circular loop she observes that the lines keep on diverging. How will you explain her observation? Q17.For the coil in the diagram below, when the switch is pressed: (a) what is the polarity of end A ? (b) which way will the compass point then ? Q18.The directions of current flowing in the coil of an electromagnet at its two ends X and Y are as shown below: ( a) What is the polarity of end X ? (b) What is the polarity of end Y ?. Q19.What does the divergence of magnetic field lines near the ends of current carrying solenoid indicate? Q.20 a) State Fleming's left - hand rule. b) A positively charged alpha particle projected towards west is deflected towards north by a magnetic field. What is the direction of magnetic field? Q.21 Write any two properties of magnetic field lines. Q.22 Draw magnetic field lines around a bar magnet. Q 23 Name and state the rule used to find the direction of magnetic field due to a straight current carrying conductor. Q 24 State two ways by which the strength of an Electromagnet can be increased. Q 25 Why do not two magnetic field lines intersect each other? Q 26 a) Name an instrument in which the directive property of a magnet is used. b) Define magnetic field. Q 27 How is the strength of magnetic field near a straight current - conductor (i) related to the strength of current in the conductor? (ii) is affected by changing the direction of flow of current in the conductor? Q 28 (a) What is the shape of a current carrying conductor whose magnetic field is concentric circles? (b) What is the direction of magnetic field lines outside a bar magnet? Q 29 Write the functions of armature and split ring in electric motor. Q 30 (a) write the conversion of energy in electric motor. (b) Give some uses of electric motor. Q 31 a) what is electromagnetic induction? b) State Fleming's right - hand rule. Q 32 Write at least two points to differentiate between AC and DC. Or Name the rule used to find the direction of induced current a nd which finger is directed towards current. Q 33 What is the current rating for i) circuit consists of electric bulbs, fans in the household? ii) circuit consists of electric geysers, air conditioners etc ? OR Give few applications of electromagnet. SECTION - B (3 Marks) Q1. (i) For the current carrying solenoid as shown below, draw magnetic field lines and giving reason explain that out of the three points P, Q and R at which point the field strength is maximum and at which point it is minimum. Also mention the polarity of the solenoid. (ii) On what factors does the magnetic field produced by a current carrying solenoid depend? Q2. In the given diagram of electric motor identify the parts X , Y and Z. Also wri te one function of each of them. OR (i) Write the principle of electric motor? (ii) How to enhance the power of an electric motor? (iii) Name some devices in which electric motors are used. Q3. Two coils of insulated copper wire are wound over a non - conducting cylinder as shown. Coil I has larger number of turns. (i) Write your observations when (a) key K is closed (b) key K is opened. (ii) When the current is passed continuously through coil I. (iii) Name the two coils used in this experiment. OR (i) With the help of an activity, explain the method of inducing electric current in a coil with a moving magnet. (ii) Two circular coils P and Q are kept close to each other, of which coil P carries a current. What will you observe in Q ? (a) I f current in the coil P is changed? (b) I f both the coils are moved in the same direction with the same speed? Give reason. Q4. (i) Can a freely suspended curr ent carrying solenoid stay in any direction? Justify your answer. What will happen when the direction of current in the solenoid is reversed? (ii) Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop antic lockwise when viewed from the top. What is the direction of magnetic field inside and outside the loop? Q5. (i)What is an electromagnet? List any two uses. (ii) You are provided with two similar bars. One is magnet and the other is iron . How will you dis tinguish between them when kept in an unknown planet neither damaging them nor using any other magnet? Q6. Magnetic field lines of two magnets are shown in fig. A and fig. B. Select the figure that represents the correct pattern of field lines. Give reasons for your answer. Also name the poles of the magnets facing each other Q7 How will the magnetic field produced at a point due to a current - carrying circular coil change if we: (a) increase the current flowing through the coil?