Physicshard · Past Paper
Two copper wires A and B have lengths in ratio 1:2 and radii in ratio 2:1. The ratio of their resistances is:
A1:2
B1:4
C1:8
D2:1
✓ Correct Answer: C — 1:8
R = ρL/(πr^2). R1/R2 = (L1/L2) * (r2/r1)^2 = (1/2) * (1/2)^2 = 1/2 * 1/4 = 1/8.
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