As a current is set up in a moving coil galvanometer, then arrange the following in sequential order.
A. Pointer attached with the coil starts rotating.
B. Pointer stops moving due to equilibrium between restoring torque and torque of coil.
C. The spring creates a restoring torque \( \tau_c = k\phi \).
D. Pointer reads a calibrated value.
E. The coil of the meter experience torque \( \tau \) = NIAB and starts rotating.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → E, A, C, B, D
In a moving coil galvanometer the coil sits in a radial magnetic field, so the current produces a deflecting torque \( NIAB \); the spring twists and produces a restoring torque \( k\phi \) that grows with the deflection. Following cause and effect:
(E) The coil of the meter experience torque \( \tau \) = NIAB and starts rotating. — the current in the coil produces this torque first.
(A) Pointer attached with the coil starts rotating. — the pointer is fixed to the coil, so it turns with it.
(C) The spring creates a restoring torque \( \tau_c = k\phi \). — as the coil turns, the spring is twisted.
(B) Pointer stops moving due to equilibrium between restoring torque and torque of coil. — this happens when \( k\phi = NIAB \).
(D) Pointer reads a calibrated value. — only the steady pointer gives a reading.
So the order is E, A, C, B, D.
NCERT (2026-27):
The Moving Coil Galvanometer – “… When a current flows through the coil, a torque acts on it. … The magnetic torque NIAB tends to rotate the coil. A spring Sp provides a counter torque \( k\phi \) that balances the magnetic torque NIAB; resulting in a steady angular deflection \( \phi \). … The deflection \( \phi \) is indicated on the scale by a pointer attached to the spring.”