JEE MAIN - Physics (2024 - 6th April Morning Shift - No. 30)
A circular coil having 200 turns, $$2.5 \times 10^{-4} \mathrm{~m}^2$$ area and carrying $$100 \mu \mathrm{A}$$ current is placed in a uniform magnetic field of $$1 \mathrm{~T}$$. Initially the magnetic dipole moment $$(\vec{M})$$ was directed along $$\vec{B}$$. Amount of work, required to rotate the coil through $$90^{\circ}$$ from its initial orientation such that $$\vec{M}$$ becomes perpendicular to $$\vec{B}$$, is ________ $$\mu$$J.
Answer
5
Explanation
$$\begin{aligned}
& W=U_f-U_i=(-M B \cos 90)-(-M B \cos 0) \\
& \Rightarrow W=M B=N i A B=5 \mu \mathrm{J}
\end{aligned}$$
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