The function of the soft iron core in the moving coil galvanometer is:

The correct answer is Option (1) → To increase the degree of radial field and magnetic field strength

In a moving coil galvanometer the coil turns between concave pole pieces round a fixed cylinder of soft iron. Soft iron has a high permeability, so it draws the field lines into itself.

This does two things: the lines pass through the core along the radii, so the field becomes radial (the plane of the coil stays along the field at every deflection and the scale is linear), and more lines are concentrated in the gap, so the field strength increases and the galvanometer becomes more sensitive.

Option (1) To increase the degree of radial field and magnetic field strength — Correct. The core makes the field more radial and stronger.

NCERT (2026-27):
The Moving Coil Galvanometer – “… The galvanometer consists of a coil, with many turns, free to rotate about a fixed axis (Fig. 4.20), in a uniform radial magnetic field. There is a cylindrical soft iron core which not only makes the field radial but also increases the strength of the magnetic field.”