A wire is coiled in the shape of a helical spring with close

A wire is coiled in the shape of a helical spring with closely spaced turns. (a) When current is passed through it, does the coil tend to lengthen, shorten, or stay the same length? (b) Does your answer depend on the current direction?

Solution

(a) When current is passed in the helical spring then North and South poles will be formed on either side of the coil. If we consider the two consecutive turns, the faces of those two consecutive turns will have unlike poles. Hence they attract each other. Due to the attraction between all the turns, the spring will be compressed.

(b) It does not depend upon the direction of the current.