JEE MAIN - Physics (2022 - 26th June Evening Shift - No. 12)
A bar magnet having a magnetic moment of 2.0 $$\times$$ 105 JT$$-$$1, is placed along the direction of uniform magnetic field of magnitude B
= 14 $$\times$$ 10$$-$$5 T. The work done in rotating the magnet slowly through 60$$^\circ$$ from the direction of field is :
14 J
8.4 J
4 J
1.4 J
Explanation
$$U = - \overrightarrow M \,.\,\overrightarrow B $$
So $${U_f} - {U_i} = - MB(1 - \cos \theta )$$
$$ = - 14J$$
So $$W = - \Delta U = 14J$$
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