A magnetised wire of moment M and length l is bent in the form of a semicircle of radius r . Then its new magnetic moment is

Question

A magnetised wire of moment M and length l is bent in the form of a semicircle of radius r . Then its new magnetic moment is (A) (2 M/π ) (B) 2M (C) (M/π ) (D) zero

Tardigrade Admin · Accepted Answer

On bending a wire its pole strength remains unchanged whereas its magnetic length changes and

l = π r

.
New magnetic moment,

M^{'} = m \times (2 r) = \frac{m \times 2 l}{π} = \frac{2 M}{π}

Q. A magnetised wire of moment $M$ and length $l$ is bent in the form of a semicircle of radius $r$ . Then its new magnetic moment is

$\frac{2 M}{π}$

$2 M$

$\frac{M}{π}$

zero

On bending a wire its pole strength remains unchanged whereas its magnetic length changes and $l = π r$ .
New magnetic moment,
$M^{'} = m \times (2 r) = \frac{m \times 2 l}{π} = \frac{2 M}{π}$

Q. A magnetised wire of moment M and length l is bent in the form of a semicircle of radius r . Then its new magnetic moment is

π2M​

2M

πM​