Explain diamagnetism and diamagnetic substances.

(N/A) Diamagnetic substances are those which have a tendency to move from the stronger to the weaker part of an external magnetic field. These substances are repelled by a magnet.
The figure shows a bar of diamagnetic material placed in an external magnetic field.
The magnetic field lines are repelled or expelled,and the field inside the material is reduced.
When placed in a non-uniform magnetic field,the bar will tend to move from a high-field region to a low-field region.
The simplest explanation for diamagnetism is as follows: Electrons in an atom orbiting around the nucleus possess orbital angular momentum. These orbiting electrons are equivalent to a current-carrying loop and thus possess an orbital magnetic moment.
Diamagnetic substances are those in which the resultant magnetic moment in an atom is zero.
When a magnetic field is applied,those electrons having an orbital magnetic moment in the same direction slow down,and those in the opposite direction speed up. Thus,the substance develops a net magnetic moment in a direction opposite to that of the applied field,resulting in repulsion.
Some diamagnetic materials are bismuth,copper,lead,silicon,nitrogen (at $STP$),water,and sodium chloride.
Diamagnetism is present in all substances,but the effect is very weak.
The magnetic susceptibility of diamagnetic substances is small and negative.