Question

The magnetic susceptibility for diamagnetic material is
A. small and negative
B. small and positive
C. large and positive
D. large and negative

Answer 1

Hint: Diamagnetic materials create an induced magnetic field in a direction opposite to an external applied magnetic field and are repelled by applied magnetic field. For diamagnetic materials their magnetic permeability is known to be little less than unity.

Complete step by step solution:
By the application of magnetic fields, some materials will not show any effects that are called nonmagnetic materials and those which show some effects are called magnetic materials. All magnetic materials magnetize in an applied external magnetic field. Depending on the direction and magnitude of magnetization and also the effect of temperature on magnetic properties, all magnetic materials are broadly classified into diamagnetic, paramagnetic and ferromagnetic materials.
Diamagnetic materials are those which are repelled by magnets and which placed in a non-uniform magnetic field, move from stronger to weaker parts of the field. These materials have no elementary magnetic dipoles. The magnetic Susceptibility of a diamagnetic substance is negative and very slightly less than one and of the order of${10}^{-5}$. There is no appreciable variation of diamagnetism with temperature that is susceptible and independent of temperature. Relative permeability of substance is less than one.
In the absence of an applied magnetic field, each Atom has net zero magnetic dipole moment. In the presence of an applied magnetic field, the angular velocities of the electronic orbit are changed. These induced magnetic dipole moments align themselves opposite to the applied field. Diamagnetism can have a big effect in superconductors and in artificial materials.
Answer - (A)

Note: When the magnetic materials are kept in an external magnetic field the electron whose orbital magnetic moments are in the same direction as that of the external magnetic field slow down and the electron's orbital magnetic moments that are in the opposite direction to that of the external magnetic field, speeds up. Thus developing magnetic moment in the direction opposite to that of the applied external magnetic field. As a result, the diamagnetic substance repels the applied field and sets itself at the right angle to the direction of the field when suspended freely in the magnetic field.