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GCSE Level Questions: Transformers

Q11. The diagram shows how electricity is supplied to consumers by the National Grid.

(a) Explain why transformer X is used in the National Grid.

Transformer X is a step-up transformer. It increases the potential difference and decreases current at which the power is transmitted. (you got no mark for saying step-up transformer - which I found odd - and yet were required to mention the stepping up of the p.d. and stepping down of the current).

This reduces (if you said stops all loss as heat energy you got no mark) thermal energy transfer to surroundings from the transmission cables, thereby increasing the efficiency of power transmission.

[4 marks]

(b) Explain why transformer Y is used in the National Grid.

Transformer Y is a step-down transformer. It decreases the potential difference to a safer value - one where electrocution is less likely to be fatal.

[2 marks]

(c) The town of Hornsdale in Australia has electricity supplied by a huge battery.

On one day the battery transferred 3.24 × 1011 J of energy to the town.

The potential difference of the town's electricity supply is 230 V.

Calculate the charge flow to the town on this day. (Give your answer to 3 significant figures).

P = IV

P/t = Q/t x V

E = QV

Q = E/V

Q = 3.24 × 1011/230

Q = 1.41 x 109 C (3 sig fig)

[4 marks]

(Total 10 marks)