The coil of a moving coil galvanometer is wound over a metallic frame

The correct answer is Option (2) → to provide electromagnetic damping

When the coil turns in the magnetic field, the metallic frame turns with it, and the magnetic flux through the frame changes. This induces eddy currents in the frame, and by Lenz's law they oppose the motion that produces them. The coil therefore stops quickly at its final deflection instead of oscillating about it. This is electromagnetic damping.

Option (1) to increase moment of inertia — Incorrect. A larger moment of inertia would only make the coil swing more slowly; it is not the purpose of the frame.

Option (2) to provide electromagnetic damping — Correct. The eddy currents in the frame damp the oscillations, so the pointer comes to rest quickly.

Option (3) to increase its sensitivity — Incorrect. The sensitivity \( NAB/k \) depends on the coil, the field and the spring, not on the frame.

Option (4) to reduce hysteresis loss — Incorrect. Hysteresis loss belongs to a magnetic core taken through repeated cycles of magnetisation; the frame is not used for that.

Note: A similar question was also asked in CUET (UG) 2025 on 15-05-2025 (Slot 2).

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Eddy Currents – “… (ii) Electromagnetic damping: Certain galvanometers have a fixed core made of nonmagnetic metallic material. When the coil oscillates, the eddy currents generated in the core oppose the motion and bring the coil to rest quickly.”