Question

a) Why are the field lines repelled when a diamagnetic material is placed in an external

uniform magnetic field .

Answer 1

the charges on dimagnetic r opposite hence they reppel

Answer 2

"Yes, the field lines repelled when a diamagnetic material is placed in an external uniform magnetic field.

This is because of the fact that diamagnetic material has paired electron and they create a magnetic field which opposes the external magnetic field. A weak magnetism is induced in the same direction.

Consider if a diamagnetic material is kept on an "external magnetic field"which is uniform in nature. The "magnetic field" around the material is given in the image.

A magnet contains dipole moment around them and the net magnetic flux of a magnet is always zero. This is the reason why the "magnetic field lines" form a continuous closed loop. But in the case of diamagnetic materials, the individual atoms do not possess any magnetic field around them."