Thank you for reporting, we will resolve it shortly
Q.
A steel wire of length $l$ has a magnetic moment $M$. It is then bent into a semicircular arc.
The new magnetic moment is
Solution:
When wire is bent, length $l = \pi r$, where $r$ is the radius of the semicircular are , $\therefore $ $r = l/ \pi$
Distance between two poles of semicircular wire = $2r = 2l/pi$
Magnetic moment of semicircular wire = $m \times 2r = m \times 2l/ \pi = \frac{2}{\pi} ml$
But $ml$ is the magnetic moment of straight wire $i.e. \, ml $ = M
$\therefore $ New magenetic moment of straight wire $i.e. \, ml $ = M
$\therefore $ New magnetic moment = 2M/$\pi$