Physics (AS & A Level) · May / June 2020 · Paper 13 · Question 34

Two copper wires are joined together and carry a current, as shown. [diagram: wire P of diameter d joined to wire Q of diameter 2d, current flowing through both] Wire P has diameter d and wire Q has diameter 2d. What is the ratio \frac{average drift speed of the free electrons in wire P}{average drift speed of the free electrons in wire Q}?

1. A\frac{1}{4}
2. B\frac{1}{2}
3. C2
4. D4

As printed in the paper