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## Homework Statement

A cylindrical copper rod of length L and cross-sectional area A is re-formed to

twice its original length with no change in volume. If the resistance between its

ends was originally R, what is it now?

## Homework Equations

R=p(L/A)

## The Attempt at a Solution

Using the above equation the answer would be 2R, however the correct answer is 4R. Why is this? I am studying for a test tomorrow and need to understand why this is so.