Case: Read the passage and answer the question.
Consider a coil C1 connected to a galvanometer G as shown. Another current-carrying coil C2 is placed next to the first coil.
Coil C2 is moved towards C1 and then held fixed. What happens to the galvanometer needle once C2 stops moving?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Comes back to zero
From the figure, C2 is joined to a battery. So it carries a steady current and sets up a steady magnetic field, part of which passes through C1. An emf, and so a current, is induced in C1 only while the magnetic flux through it changes. This happens only while there is relative motion between the coils.
Option (1) Goes on deflecting in the direction it was — Incorrect. A deflection needs an induced current; once C2 is at rest, the flux through C1 is constant and no current is induced.
Option (2) Deflects in the opposite direction — Incorrect. The opposite deflection appears when C2 is moved away from C1 and the flux decreases. A coil held fixed does not change the flux.
Option (3) Stays deflected where it was — Incorrect. The galvanometer shows the current at each instant; with no emf there is no current to keep the needle deflected.
Option (4) Comes back to zero — Correct. The deflection lasts only as long as C2 moves. When it stops, the flux through C1 stops changing, the induced emf becomes zero and the needle returns to zero.
NCERT (2026-27):
The Experiments of Faraday and Henry – “… The steady current in the coil C2 produces a steady magnetic field. As coil C2 is moved towards the coil C1, the galvanometer shows a deflection. This indicates that electric current is induced in coil C1. When C2 is moved away, the galvanometer shows a deflection again, but this time in the opposite direction. The deflection lasts as long as coil C2 is in motion.”