Correct answer is : 28
We know that, pole strength \(\mathrm{m}=\frac{\mathrm{M}}{\mathrm{l}}\)
\(
\begin{aligned}
=\mathrm{M}=\mathrm{ml}
\end{aligned}
\)
\(
\begin{aligned}
\Rightarrow \mathrm{M}=\mathrm{m} \times 2 \mathrm{r}
\end{aligned}
\)
If r is the radius of semicircle formed by bending the strip of length 1 , then
\(
\begin{aligned}
\pi \mathrm{r}=1
\end{aligned}
\)
\(
\begin{aligned}
\mathrm{r}=\frac{1}{\pi}
\end{aligned}
\)
Distance b/w the poles ; \(2 \mathrm{r}=\frac{21}{\pi}\)
Hence, new magnetic moment \(\left(\mathrm{M}^{\prime}\right)\)
\(
\begin{aligned}
M^{\prime}=m \times 1
\end{aligned}
\)
\(
\begin{aligned}
=\frac{M}{l} \cdot \frac{2 l}{\pi}=\frac{2 M}{\pi}=\frac{2 \times 44}{(22 / 7)}
\end{aligned}
\)
\(
\begin{aligned}
=28 \mathrm{Am}^2
\end{aligned}
\)
