Magnetism: Moving Coil Galvanometer MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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Moving Coil GalvanometerHardQuestion 20180

Question

In a moving coil galvanometer, the deflection is proportional to current because:

A
The restoring torque is constant
B
The spring exerts constant force
C
The magnetic torque and spring restoring torque balance in proportion to I
Correct
D
The field is non-uniform

The magnetic torque and spring restoring torque balance in proportion to I

At equilibrium: NIAB = kφ → φ = (NAB/k)I. The linear relationship between φ and I holds when the radial field keeps sinθ = 1 always.