A magnetic needle lying prllel 2 a magnetic field reqs W units of work to turn it t

A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60°. The torque needed to maintain the needle in this position will be

ans root3 W

how?whts the formula?

see W=change in potential energy.

IWI=UBcos60=UB/2  .......1

now torque=UBsin=

substitute U from 1 to get the answer