| Directions: In the following questions, a statement of Assertion [A] is followed by a statement of Reason (R). Mark the correct choice as: |
| Assertion [A]: The ability of a material to permit the passage of magnetic lines of force through it is called magnetic permeability. |
| Reason (R): For a perfect diamagnetic substance, permeability is always one. |
A) Both Assertion [A] and Reason (R) are true and Reason (R) is the correct explanation of Assertion [A]
B) Both Assertion [A] and Reason (R) are true but Reason (R) is not the correct explanation of Assertion [A]
C) Assertion [A] is true but Reason (R) is false
D) Assertion [A] is false and Reason (R) is also false
Correct Answer: C
Solution :
(c) For a perfectly diamagnetic substance, \[B={{\mu }_{0}}(H+1)=0\therefore l=-H\]. Therefore, \[{{\chi }_{m}}=\frac{1}{H}=-1\] Therefore relative permeability \[{{\mu }_{r}}=1+{{\chi }_{m}}=1-1=0\] \[\therefore \mu ={{\mu }_{0}}{{\mu }_{r}}=zero.\] i.e. for a perfect diamagnetic material permeability is zero.
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