Question

A steel wire of length $l$ has a magnetic moment $M$. It is bent in $L$-shape (figure). The new magnetic moment is

• A. $M$
• B. $\frac{M}{\sqrt{2}}$
• C. $\frac{M}{2}$
• D. $2M$

Answer 1

Answer: (B)

$\frac{M}{\sqrt{2}}$

Magnetic moment, $M=ml$
$\frac{M}{l}=m$, where $m$ is the polestrength.
Therefore distance between poles $=\sqrt{{\left(l/2\right)}^2+{\left(l/2\right)}^2}=\frac{l}{\sqrt{2}}$
So, $M^{\prime }=\frac{ml}{\sqrt{2}}=\frac{M}{\sqrt{2}}$