Q: A thin diamagnetic rod is placed vertically between the poles of an electromagnet . When the current in electromagnet is switched on , then the diamagnetic rod is pushed up , out of horizontal magnetic field . Hence the rod gains gravitational potential energy .The work required to do this comes from
(a) the lattice structure of the material of the rod
(b)the induced electric field due to the changing magnetic field
(c)the magnetic field
(d) the current source
Ans: (d)
Sol: The energy provided by current source is converted into gravitational potential energy .