(a) The primary coil of a transformer is connected to the 230 V a.c. mains supply.

1. (a)(i)Describe how the transformer operates.[3]
2. (a)(ii)The output voltage of the transformer is alternating and cannot be used directly as a d.c. power supply. In the space below, draw the symbol of a circuit component that allows the current to pass in only one direction and state the name of the component.[2]
3. (b)Fig. 9.1 shows a d.c. power supply being used to charge a rechargeable battery. [Figure 9.1] The rechargeable battery is in series with the d.c. power supply and a 5.2Ω resistor. The e.m.f. of the power supply is 5.0V.
4. (b)(i)Explain what is meant by e.m.f.[2]
5. (b)(ii)The e.m.f. of the power supply and the e.m.f. of the battery act against each other in opposite directions in the circuit. The e.m.f. of the battery is 3.7 V.
6. (b)(ii) 1.Calculate the resultant e.m.f. in the circuit.[1]
7. (b)(ii) 2.Calculate the current in the circuit.[2]
8. (b)(ii) 3.The current in the circuit remains constant as the battery is charged. Calculate the charge that passes through the resistor in 1.5 hours.[3]
9. (c)A battery charger has a plastic casing and double insulation. The battery charger is not earthed. Explain why it is not necessary for the battery charger to be earthed.[2]

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