A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnetic is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains horizontal potential energy. the work required to do this comes from

Options

A. The lattice structure of the material of the rod
B. the magnetic field
C. the current source
D. the induced electric field du to the changing magnetic field

Answer

C

Explanation

c) As the sourceof current is switched on, a magnetic field sets up in between the poles of the electromagnet. As we know that a diamagnetic substances when placed in a magnetic field acquires a feeble magnetism opposite to the direction of the magnetic field.
Also, in the presence of the field (non-uniform), these substances are attracted towards the weaker field, i.e. they move from stronger to weaker magnetic field.
Due to these reasons, the rod is repelled by the field produced to the current source. Hence, it is pushed up, out of horizontal field and gains gravitational potential energy.