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A thin magnetic needle is placed in a magnetic field of
200 G with its axis at 30° to the direction of the field.
Find the magnetic moment of the needle if it experiences
a torque of 0.012 Nm in this field.
Options:
200 G with its axis at 30° to the direction of the field.
Find the magnetic moment of the needle if it experiences
a torque of 0.012 Nm in this field.
Solution:
2698 Upvotes
Verified Answer
The correct answer is:
$1.2 \mathrm{Am}^2$
Magnetic field, $\mathrm{B}=200 \mathrm{G}=200 \times 10^{-4} \mathrm{~T}$
We have
Torque $\tau=m B \sin \theta$
$$
\begin{aligned}
& 0.012=\mathrm{m} \times 200 \times 10^{-4} \times \sin 30^{\circ} \\
& \mathrm{m}=0.012 \times 10^2 \\
& \mathrm{~m}=1.2 \mathrm{Am}^2
\end{aligned}
$$
We have
Torque $\tau=m B \sin \theta$
$$
\begin{aligned}
& 0.012=\mathrm{m} \times 200 \times 10^{-4} \times \sin 30^{\circ} \\
& \mathrm{m}=0.012 \times 10^2 \\
& \mathrm{~m}=1.2 \mathrm{Am}^2
\end{aligned}
$$
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