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.