Physics (AS & A Level) · Oct / Nov 2025 · Paper 14 · Question 34

A copper wire of length 2 m has a circular cross-section. There is a constant current in the wire when it is connected to a mobile phone in order to charge the battery. The wire has a fault. A 1 m length of the wire has half the diameter of the other 1 m length. The power dissipated in the thicker length of wire is P. What is the power dissipated in the thinner length of wire?

1. A\frac{1}{4}P
2. B\frac{1}{2}P
3. C2P
4. D4P

As printed in the paper