An electricity and magnetism problem by Jeet Dholakia
Electricity and Magnetism
Level
2
Wires A and B are made of same materials.B has twice the diameter and twice the length of A. If A has resistance 50 ohms than B has resistence?
100 ohms
25 ohms
12.5 ohms
50 ohms
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1 solution
Let length of A be l and radius be r. Then, for B: length = 2l and radius = 2r. since the ratio of R for the 2 wires is effectively: length/Area, R1:R2 = 2/(2)^2 = 1/2. Since R1 = 50, R 2 = 25