Question

If a bar magnet of moment M is bent as are its magnetic moment

• A. decreases
• B. increases
• C. does not change
• D. may change

Answer 1

The correct option is A decreases

Given: A bar magnet of moment M

Solution: As magnet pole strength is given by,

$m=\frac{M}{L}$

where, M is the magnetic moment and L is the effective length.

After bending the effective length becomes L' (say),

then the new magnetic moment will be:

$M^{\prime }=m{L}^{\prime }$

So, $M^{\prime }=\frac{M}{L}\times L^{\prime }$

As, $\frac{L^{\prime }}{L}$ < 1

Hence, $M^{\prime }<M$, So the correct option is (A)