AP EAPCET 24-Aug-2021 Shift 1 Paper

Given that, magnetic moment, M=2JT−1
Magnetic field, B=0.1T
Since, magnetic moment is aligned in the direction of magnetic field, i.e. initial angle,
θ1=0°
When magnet is normal, then final angle, θ2=90°
Using relation for work done,
W=−MB(cos‌θ2−cos‌θ1)
Substituting the values, we get
W=−2×0.1(cos‌90°−cos‌0°)
=−2×0.1(0−1)=0.2J
Hence, 0.2J work will be done to rotate a magnet from 0° to 90° angle with in magnetic field.