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.                 \[\vec{H}=\frac{{\vec{\beta }}}{{{\mu }_{0}}}-\vec{I}\] \[=I{{\chi }_{m}}H\] Magnetic susceptibility of diamagnetic substance is negative. \[I=-H\] \[OC'=\text{retentivity}\] \[OC''=\text{coercivity}\] \[{{\mu }_{r}}=\text{slightly}\,\text{less}\,\text{than}\,\text{one}\] \[=1+{{\chi }_{m}}\] \[{{\chi }_{m}}=-\upsilon e\]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.