PHYSICS
posted by nat .
A wire of initial length Lo and radius rO has a measured resistance of 1.0 ohm. the wire is drawn under tensil stress and to a new uniform radius of 0.25rO. what is the new resistance of the wire? i know the answer is 256 ohm but i have no clue how to get the answer can anyone help me?

The cross sectional ara is reduced by a factor (1/4)^2 = 1/16. The length must increase by a factor of 16 to keep the total volume constant.
(since Volume = Area x Length)
The resistance is proportional to Length/Area^2, so that increases by a factor of 16/(1/16) = 16 * 16 = ?