Physics (AS & A Level) · Oct / Nov 2018 · Paper 12 · Question 35

A wire of length L has resistance R. The cross-section of the wire is circular with radius r. A second wire, also of circular cross-section, and of the same material, has resistance 1/2 R. What could be the radius and the length of the second wire?

1. Aradius r/2, length L/2
2. Bradius r/√2, length L/2
3. Cradius r√2, length 2L
4. Dradius 2r, length 2L

As printed in the paper