4.4 Practical Electricity | Cambridge O Level Physics Topic Questions 2023

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4 marks

A teacher uses a power supply in a metal case. The circuit for the power supply includes a fuse.

(i)

Draw the electrical symbol for a fuse.

[1]

(ii)

The metal case of the power supply is earthed. A fault occurs and a live wire touches the metal case.

Explain how earthing the metal case protects the teacher.

[3]

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3 marks

The power supply circuit includes a transformer. Its input voltage is 240 V. There are 960 turns on the input coil and 64 turns on the output coil.

Calculate the output voltage of the transformer.

output voltage = ..................................................... V

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3 marks

Fig. 8.1 shows a circuit containing a 230 V a.c. supply connected to a television and two lamps.

q8-cie-ol-physics-specimen-paper-2-sq

Fig. 8.1

In normal operation, both switches are closed. The power supplied to each lamp is 40 W and the power supplied to the television is 120 W.

Calculate, in normal operation:

(i)

the total number of kilowatt-hours (kW h) of energy supplied to the circuit in 1.0 hour

number of kW h = .......................................................... [1]

(ii)

the current in each lamp.

current = ....................................................... A [2]

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2 marks

Explain why the switches are placed in the live wire and not in the neutral wire.

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1 mark

State one advantage of connecting the two lamps in parallel in this circuit.

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Practical Electricity (Cambridge O Level Physics)