Inductance is parameter of electrical engineering. In this article, we will discuss inductance and factors affecting inductance.

Inductance is the name given to the property of a circuit where by there is an e.m.f. induced in to the circuit by the change of flux linkages produced by a current change. When the e.m.f. is induced in the same circuit as that in which the current is changing, the property is called self inductance.

It is denoted by capital letter L.

When the e.m.f. is induced in a circuit by a change of flux due to current changing in an adjacent circuit, the property is called mutual inductance, M.

The unit of inductance is the henry H.

A circuit has an inductance of one henry when an e.m.f. of one volt is induced in it by a current changing at the rate of one ampere per second.

Induced e.m.f. in a coil of N turns,


Where is the change in flux in Webers, and dt is the time taken for the flux to change in seconds. Induced e.m.f. in a coil of inductance L henrys,

factors affecting inductance

Where dI is the change in current in amperes and dt is the time taken for the current to change in seconds. The minus sign in each of the above two equations remind us of its direction (given by Lenz’s law).

Factors Affecting Inductance

The greater the self-induced voltage, the greater the self inductance of        the coil and hence larger is the opposition to the changing current. According to Faraday’s laws  of electromagnetic induction, induced voltage   in a coil depends upon the number of turns (N) and the  rate of change of flux (dφ/dt)  linking the coil.  Hence,  the inductance  of a coil depends upon these factors, viz :

  • Shape and number of turns.
  • Relative permeability of the material surrounding the coil.           
  • The speed with which the magnetic field changes.