What is the main function of soft iron core used in a moving coil galvanometer?

Explanation

This makes the magnetic field radial. In such a magnetic field the plane of the coil is always parallel to the direction of magnetic field. Due to which the galvanometer becomes linear.
(ii) This increases the strength of magnetic field due to the crowding of the magnetic lines of forces through the soft iron core which increases the sensitiveness of galvanometer.