An induction coil is a device that converts a low voltage direct current (DC) into a high voltage alternating current (AC) pulse using the principle of electromagnetic induction.
It consists of two coils—a primary coil with few turns connected to the low voltage DC source, and a secondary coil with many turns. When current in the primary coil is rapidly switched on and off (usually by an interrupter), the changing magnetic flux through the secondary coil induces a high voltage across it according to Faraday’s law.
This high voltage output is often used to generate sparks, for example, in ignition systems or early X-ray tubes.
Thus, the induction coil steps up voltage by rapidly changing the current and thereby the magnetic flux linking the coils.
