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Questions on Electric Circuits

Q1.

(a) A wooden pencil is sharpened at both ends. It is connected to two bulbs and a battery as shown. The two crocodile clips are connected to the wooden part of the pencil. Why do the two bulbs not light up?

A: The battery is connected the wrong way round.

B: The bulbs are connected the wrong way round.

C: The wood is a conductor.

D: The wood is an insulator.

1 mark

(b) The two crocodile clips are now connected to the 'lead' (graphite) of the pencil as shown. The two bulbs light up dimly. Why do the two bulbs light up?

1 mark

They light up because graphite is a conductor of electricity - not a good one, but it does conduct. That means we now have a complete circuit.

The reason why the bulbs are only dim is that graphite is a poor conductor.

(c) One crocodile clip is connected to the pencil 'lead' (graphite) and the other one is connected to the wood. Which of the bulbs, if any, lights up?

Neither will light up

1 mark

Maximum 3 marks