Question

If a copper wire is stretched so that its length increases by 20% then what is the percentage increase in its resistance (assuming its volume remaing constant) ?

A. 10%

B. 21%

C. 44%

D. 120%

Answer 1

If a copper wire is stretched so that its length increases by 20% then what is the percentage increase in its resistance would be 44%.

What is the percentage increase?

Stretching the wire increases its length by 20%, but it also affects the cross-sectional area. To maintain the same volume, the cross-sectional area must decrease proportionally. This decrease in area counteracts some of the increase in length, but not entirely.

So, we would have the following value;

2 * 0.2/100 * 100

= 0.44

= 44%