February 28, 2017

Homework Help: College Physics

Posted by Andrew on Thursday, November 24, 2011 at 6:55am.

A wire P has resistance R. If the wire is stretched and its length is increased by 10%, what would be the percentage change in its resistance? (Assume the density of the wire remains constant)

A) - 10%
B) 0 %
C) 10%
D) 20%

My thoughts:
Since resistance is R = resistivity x length / cross-sectional area of wire, when the length increases by 10%, R should increase by 10%. Cross sectional area doesn't change as the wire is stretched, as the atoms are horizontally pulled apart in the direction of the stretch and have a wider spacing between each other.

However, the answer given is D.

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