Q150 / 160 · TS EAMCET 2022 (19 Jul Shift 1) · Physics
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.
- Correct answerA$1.2 \mathrm{Am}^2$
- B$12.0 \mathrm{Am}^2$
- C$0.6 \mathrm{Am}^2$
- D$6.0 \mathrm{Am}^2$
Solution
Magnetic field, $\mathrm{B}=200 \mathrm{G}=200 \times 10^{-4} \mathrm{~T}$
We have
Torque $\tau=m B \sin \theta$
$$
\begin{aligned}
& 0.012=\mathrm{m} \times 200 \times 10^{-4} \times \sin 30^{\circ} \\
& \mathrm{m}=0.012 \times 10^2 \\
& \mathrm{~m}=1.2 \mathrm{Am}^2
\end{aligned}
$$
Hence, the correct answer is option: 'A'.