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GCSE Standard Questions: Electric Circuits

Q15.

(a) Lex investigated how the current in a series circuit varied with the resistance of a variable resistor. The diagram below shows the circuit he used:

This graph shows his results:

(i) The battery had a power output of 230 mW when the resistance of the variable box resistor was 36 Ω.

Determine the potential difference across the battery.

[4 marks]

(ii) Lex concluded: 'the current in the circuit was inversely proportional to the resistance of the variable resistor.'

Explain how the results on his graph show that he is correct.

[2 marks]

(b) The diagram below shows a circuit with a switch connected incorrectly.

Explain how closing the switch would affect the current in the variable resistor.

[3 marks]

(Total 9 marks)