What are the uses of an induction coil?

Why a capacitor is used in the primary circuit of an induction coil?

A capacitor is used in the primary circuit of an induction coil.

Answer the following questions: A capacitor is used in the primary circuit of an induction coil.

The mutual inductance of an induction coil is 5H . In the primary coil, the current reduces from 5 A to zero in 10^(-3)s . What is the induced emf in the secondary coil