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GCSE Level Questions: Transformers

Q10. The diagram shows a portable power supply.

(a) The portable power supply has an alternator connected to a transformer.

The transformer can be adjusted to have different numbers of turns on the secondary coil.

Suggest why.

[2 marks]

(b) A lamp is connected to the power supply.

The lamp requires an input potential difference of 5.0 V.

The alternator generates a potential difference of 1.5 V.

The primary coil of the transformer has 150 turns.

Calculate the number of turns needed on the secondary coil.

[3 marks]

(c) The diagram below shows the inside parts of the alternator.

The handle of the alternator is turned, causing the coil to rotate.

(i) Explain why an alternating current is induced in the coil.

[5 marks]

(ii) Suggest the purpose of the slip rings.

[1 mark]

(iii) The alternator from the portable power supply is disconnected from the transformer and lamp. Explain why the handle of the alternator becomes much easier to turn.

[3 marks]

(Total 14 marks)