Inductors

Inductors store energy in a magnetic field. The magnetic field is created by passing current through a coil of wire, as is done in an electromagnet such as those used to lift scrap iron.
In electric circuits inductors often play the role of smoothing devices that reduces current variations.But when the current is forced to change abruptly, the inductor generates a large induced voltage- - large enough to cause a spark in the extreme case of an automobile ignition circuit.
This two terminal device consists of a wire coil wound around a core.The core may be cylindrical or it may be doughnut-shaped. The coil has N turns , insulated from one another and from the core.When the wire carries the current i, a magnetic field is created in the space around the coil and becomes concentrated within the core.Like an electric field, the magnetic field holds energy that comes from the source that established the field.hence,

An inductor stores energy in a magnetic field produced by current through a wire coil.The strength of the field expressed in terms of magnetic flux through the core.The proportionality constant L is the inductance which is measured in henrys (H).

V=L* di/dt