Inductance Formula

When an electric current flow through a conductor, it creates a magnetic field around it. A changing current creates a varying magnetic field, so that the magnetic flux is also varying inducing an electromotive force. Inductance describes the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The change of current induces an inverse electromotive force.

The inductance forms part of the impedance of the circuit; that is, its existence implies a certain resistance to the circulation of the current. The formula for magnetic inductance is defined as the quotient between the magnetic flux in the element, and the electric current circulating through the element.

Inductance = Magnetic flux* Number of coil turns / current intensity

The equation is written

L = ΦN/I

We have

L = Inductance

Φ = Magnetic flux

N = Number of coil turns

I = current intensity

Inductance Questions:

1) An inductor coil has 550 turns of copper wire that produces a magnetic flux of 20 Wb when passing a direct current of 5 amps. Calculate the coil's self-inductance.

Answer: We use the above equation to achieve self-inductance, where Φ = 20 Wb, N = 550, I = 5 A

L = ΦN/I

L = (20 Wb)(550)/5A

L = 2200 H.

2) An inductor coil has 1000 turns of copper wire that produces a magnetic flux of 300 mWb when passing a direct current of 8 amps. Calculate the coil's self-inductance.

Answer: We use the above equation to achieve self-inductance, where Φ = 300 mWb = 0.3 Wb, N = 1000, I = 8 A

L = ΦN/I
L = (0.3 Wb)(1000)/8A
L = 37.5 H.