15 © UCLES 2017 0625/23/M/J/17 [Turn over 31 A battery, an ammeter, a switch, a lamp and a resistor are connected together in a circuit. A With the switch open, the ammeter reads 2.4 A. When the switch is closed, this reading increases to 4.0 A. What is the current through the resistor with the switch closed? A 0 A B 1.6 A C 3.2 A D 6.4 A 32 A student connects a variable potential divider (potentiometer) circuit. R S T V 12 V What happens to the reading on the voltmeter as the sliding terminal T is moved from R to S? A It decreases from 12 V to 0 V. B It increases from 0 V to 12 V. C It remains at 0 V. D It remains at 12 V. 16 © UCLES 2017 0625/23/M/J/17 33 The diagram shows a circuit used to make a light detector. A X Y One component is connected between X and Y. Which component causes the ammeter reading to increase when the light gets brighter? A B C D 34 A truth table for a type of logic gate is shown. input 1 input 2 output 0 0 0 0 1 1 1 0 1 1 1 1 Which type of logic gate is it? A AND B NOR C NOT D OR 35 In which device is a split-ring commutator used, and what is its purpose? device purpose A a.c. generator to change the direction of the current in the coil as it turns B a.c. generator to change the output current from d.c. into a.c. C d.c. motor to change the direction of the current in the coil as it turns D d.c. motor to change the input current from a.c. into d.c. 17 © UCLES 2017 0625/23/M/J/17 [Turn over 36 What is the purpose of a relay? A to change a large voltage into a small voltage B to change a small voltage into a large voltage C to use a large current to switch on a small current D to use a small current to switch on a large current 37 When a source of D -particles is directed towards a thin metal foil they become scattered. Which observation of this experiment provides evidence for a small charged nucleus? A A small proportion of the D -particles come straight back from the foil towards the source. B A small proportion of the D -particles pass straight through the foil. C Some of the D -particles are deflected by an angle of less than 90 ° D Some of the D -particles follow a curved path after leaving the foil. 38 Which description of a neutral atom of copper is correct? A a nucleus surrounded by electrons B a nucleus surrounded by molecules C electrons surrounded by a nucleus D electrons surrounded by molecules 39 A sample of radioactive isotope is decaying. The nuclei of which atoms will decay first? A It is impossible to know because radioactive decay is random. B It is impossible to know unless the age of the material is known. C The atoms near the centre will decay first because they are surrounded by more atoms. D The atoms near the surface will decay first because the radiation can escape more easily. 18 © UCLES 2017 0625/23/M/J/17 40 A student determines the half-life of a radioactive isotope. The student uses a detector over five minutes and plots a graph showing how the count rate shown on the detector varies with time. The count rate due to background radiation is 30 counts per minute. 250 200 150 100 50 0 0 1 2 3 4 5 count rate counts / minute time / minutes What is the half-life of this isotope? A 0.30 minutes B 1.2 minutes C 1.5 minutes D 5.0 minutes