A magnetic wire of dipole moment 4$\pi$ A-m² is bent in the form of semicircle. The new magnetic moment is

If length of wire is 2/, then magnetic moment,

$M=m\times 2l=4\pi \mathrm{A}-{\mathrm{m}}^2\text{ (given) }$

As wire is bent in the form of semicircle, effective distance between the ends is 2r.
So, new dipole moment,  $M\text{'}=m\times 2r$

As,  $\pi r=2l$

$\Rightarrow r=2l/\pi$

So,   $M\text{'}=m\times 2\times \frac{2l}{\pi }=\frac{2}{\pi }(m\times 2l)$

$=\frac{2}{\pi }M=\frac{2}{\pi }4\pi =8 \mathrm{A}-{\mathrm{m}}^2$