An inductor, also called a choke, coil or reactor is a passive electronic component with two terminals. It is a component that stores energy in the form of a magnetic field when electric energy flows through it. An insulator has a coil of wire wound around a core. When there is a change in electric current passing through the coil, the time-varying magnetic field induces an electromotive force (emf) in the conductor. The emf induced is directly proportional to the rate of change of current, with respect to time.
As already mentioned, the emf induced is proportional to the change in current with time. The proportionality constant in the relation is called Inductance. Inductors are described by their inductance. Inductance is defined as the ratio of the emf created to the rate of change of current. Inductance also depends on the magnetic permeability of the core material, number of turns of the coil, length of the coil in coaxial direction, cross-sectional area of the coil and the space that is given between the turns of the coil. The SI unit of inductance is Henry (H).
Property 1: Inductors store electrical energy in the form of magnetic energy. The formula for energy stored in the magnetic field is equal to E = (½)LI2, where L is the inductance and I is the current.
Property 2: Inductors allow only direct current (DC) to pass through it while blocking the alternating current (AC). These types of inductors are called chokes.
Property 3: Inductors consume reactive power.
Property 4: In a pure inductive circuit, the current lags voltage by 900.
Property 5: Inductors oppose current change for alternating current.