Magnetic moment of the loop,
Magnetic Field,
(a) Torque acting on the loop,
(b) Axis of rotation coincides with the torque and since torque is in j - i direction or parallel to Q S.Therefore, the loop will rotate about an axis passing through Q and S as shown along-side :
Angular acceleration,
Where I = moment of inertia of loop about Q S.
(From theorem of perpendicular axis)
∴ Angle by which the frame rotates in time Δt is