question_answer

The variation of the intensity of magnetisation (I) with respect to the magnetising field (H) in a diamagnetic substance is described by the graph:

A)  OC         

B)  OD

C)  OA

D)  OB

Correct Answer: A

Solution :

 Magnetisation (I) = magnetic moment per unit volume of a magnetized substance. \[\overset{\to }{\mathop{H}}\,=\frac{\overset{\to }{\mathop{\beta }}\,}{{{\mu }_{0}}}-\overset{\to }{\mathop{I}}\,\] \[=I{{\chi }_{m}}H\] Magnetic susceptibility of diamagnetic substance is negative. \[I=-H\] \[OC=\] retentivity \[OC=\]coercivity                               \[{{\mu }_{r}}=\] slightly less than one \[=1+{{\chi }_{m}}\] \[{{\chi }_{m}}=-\upsilon e\] also less than one\[\tan \theta =\frac{I}{H}={{\chi }_{m}}\]                \[\theta <45\]if \[\theta =45\] \[{{\chi }_{m}}=-1\] \[{{\mu }_{r}}=0\]not possible                             If\[\theta >45{{\chi }_{m}}>-1{{\mu }_{r}}=-\upsilon e\]not possible         Hence, OC is correct,