Question

When a current-carrying coil of N turns and area A, carrying current I, is placed in a magnetic field B, the magnitude of the magnetic torque acting on it is:

Options

• \[\tau = \frac{NIAB}{\sin\theta}\]

• \[\tau = N I A B \sin\theta\]

• \[\tau = N I A B \cos\theta\]

• \[\tau = \frac{IAB\sin\theta}{N}\]

Answer 1

The deflecting couple on the coil is \[\tau = NIAB\sin\theta\] In the radial field of the galvanometer, \(\theta = 90°\) at all positions, so \(\sin\theta = 1\) and the torque simplifies to \(\tau = NIAB\).