Assertion : When a magnetoflength Land magnetic moment Mis bent to forma semicircular arc, the new magnetic moment is `2M//pi`
Reason : Magnetic moment of a magnet depends only upon the distance between the poles of the magnet.

Options

A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are true but Reason is not correct explanation of Assertion
C. If Assertion is true but Reason is false
D. If both Assertion and Reason are false.

Answer

C

Explanation

Consider a magnet of length L, and pole strangth m.
Its magnetic moment = m L
Next bend it into a semicircular are of radius R
Then `R=L/pi and `
the amgnetic moment `M_1=m2R=(2mL)/pi=(2M)/pi`
The assertion is true. The magnetic moment which depends upon the pole strength and the distanse between the poles is calculated as `(2M)/pi`. The reason is false. It is not only the distance between poles but also the pole strength which determines the magnetic moment