I have a physics exam this upcoming week and I was provided with a study guide w

Question

I have a physics exam this upcoming week and I was provided with a study guide with numerous question on the material being covered. I have finished the majority of it, however I'm having a few issues with a specific question. If anyone could clarify and help me towards and answer it'd be greatly appreciated.

When a voltage difference is applied to a piece of copper wire, a 4.0 mA current flows. If the copper wire is replaced with a silver wire with twice the diameter of the copper wire, how much current will flow through the silver wire. The lengths of both of the wires are the same, and the voltage difference remains unchanged.

A. 16 mA

B. 8.5 mA

C. 15 mA

D. 17 mA

E. 4.2 mA

Thank you in advance for any help provided!

Explanation / Answer

= RA/l

Ag/Cu = 1.59/1.68 = 0.9464

RAg/RCu = 0.9464* 22 (as new Area=2^2 * old Area)

IAg/ICu = RCu/RAg = 0.9464 * 4

IAg = 4**0.9464*4 15mA

hence answer is C

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