Induction coil is an electrical device, often called a transformer, that produces high-voltage alternating current from lower voltage alternating current. An induction coil has two sets of wire windings—a primary winding and a secondary winding. The secondary winding has more turns of wire than the primary one. If the current flowing in the primary winding is interrupted repeatedly, it creates a changing magnetic field around both windings. The changing magnetic field, in turn, creates an electromotive force in the secondary winding that “pushes” electric current. This force acts with greater strength in wires with many windings. Thus, the secondary winding has a higher voltage than the primary winding.
The way the current supplied to the primary winding is interrupted depends on the type of coil. For example, induction coils are used to fire the spark plugs in some automobile engines. The primary current in such coils is interrupted by mechanical breaker points that are opened and closed by the car’s distributor. In induction coils used to ignite gas stoves, jet engines, and oil burners, the primary current is broken by a magnetic vibrator similar to the type used in doorbells. Some induction coils use a special electronic circuit to interrupt the primary current.
