SAT Subject Physics Practice Question 83: Answer and Explanation

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Question: 83

1. A wire made of brass and a wire made of silver have the same length, but the diameter of the brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater than the resistivity of silver. If RB denotes the resistance of the brass wire and RS denotes the resistance of the silver wire, which of the following is true?

A. RB = RS
B. RB = RS
C. RB = RS
D. RB = RS
E. RB = RS

Correct Answer: A


Let ρS denote the resistivity of silver and let AS denote the cross-sectional area of the silver wire. Then

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