To study the phenomenon of electromagnetic induction.
The phenomenon of electromagnetic induction is the existence of an induced current in a circuit (such as a coil) placed in a region where the magnetic field motion changes with the time. The magnetic field may change due to relative motion between coil and magnet placed near the coil as shown in the Fig. 1. We know that a current-carrying conductor also produces magnetic field that changes with a change in the current flowing through it. Thus if a coil is placed near to a current-carring conductor, an induced current in the coil may setup due to a change in the current through the current-carrying conductor.
Fig. 1: Moving a magnet towards a coil sets up a current in the coil circuit,
as indicated by deflection in the galvanometer needle.
Source: NCERT class X lab manual