Auto-Inductance

Current flowing in any isolated circuit produces a magnetic field in the circuit. On changing the current, the magnetic flux also changes, inducing an emf.

This emf is called self-induced emf, and the phenomenon is self-inductance.

According to Lenz's law, the self-induced emf opposes any change in the current flowing through the circuit.

Using Faraday's law, the self-induced emf in the circuit can be expressed in terms of magnetic flux.

Also, the magnetic flux in the circuit is proportional to the current flowing through it, and the proportionality constant is known as the self-inductance of the corresponding circuit.

The self-inductance is purely a geometric factor that needs to be calculated separately for all the geometries of the conductor.

Using Faraday's law and the definition of self-inductance, the induced emf can be expressed in terms of self-inductance.

For a straight current-carrying conductor, Ampère's law gives the magnetic field inside the conductor. The magnetic flux is calculated upon integrating the magnetic field over the cross-sectional area. Thus, the self-inductance of the straight current-carrying conductor can be estimated.