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Question: Answered & Verified by Expert
A current ' $\mathrm{I}$ ' is flowing in a conductor of length ' $\mathrm{L}$ ' when it is bent in the form of a circular loop, its magnetic moment will be
PhysicsMagnetic Effects of CurrentMHT CETMHT CET 2021 (23 Sep Shift 1)
Options:
  • A $\frac{\mathrm{IL}}{4 \pi^2}$
  • B $4 \pi \mathrm{IL}^2$
  • C $\frac{4 \pi}{\mathrm{IL}^2}$
  • D $\frac{\mathrm{IL}^2}{4 \pi}$
Solution:
2478 Upvotes Verified Answer
The correct answer is: $\frac{\mathrm{IL}^2}{4 \pi}$
$$
\begin{aligned}
& \mathrm{L}=2 \pi \mathrm{r} \\
& \therefore \mathrm{r}=\frac{\mathrm{L}}{2 \pi}
\end{aligned}
$$
Area of the loop, $\mathrm{A}=\pi \mathrm{r}^2=\pi \frac{\mathrm{L}^2}{4 \pi^2}=\frac{\mathrm{L}^2}{4 \pi}$
Magnetic moment, $\mathrm{M}=\mathrm{IA}=\frac{\mathrm{IL}^2}{4 \pi}$

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