Inductance: Overview, Questions, Preparation

In simple terms, inductance is referred to as the property of a conductor that opposes the change in the flow of electric current by introducing an electromotive force. Such devices who have the specific properties of inductance are known as inductors. Unit of measurement for inductance is Henry (H) and the symbol used to denote inductance is L.

Inductance is primarily classified into two types:

1. Self-Inductance

It is the property of a conductor to show resistance towards the current flowing through it and occurs when a changed current in the coil induces electromotive force (EMF). General formula to represent self-inductance is:

ε=−L. dI/dt​

Where,

Ε = induced EMF

L = self-inductance

dI/dt​ = rate of change in the current

2. Mutual Inductance

Mutual Inductance is the property of a coil to oppose the change in current flowing from a neighboring coil. It occurs when changing the current in one coil induces EMF in the second coil.

Mathematical Respresentation:

E2​=−MdI1/dt

Where,

ε2 = EMF induced in the neighboring coil

dI1​​/dt = rate of change of current in the first coil

M = Mutual Inductance (between first and second coil)

It’s important to note that inductance is directly proportional to magnetic flux of the coil. Lets understand this through a mathematical formula:

Self-Inductance

L=NΦ/I

Where,

L = self-inductance

N = number of turns

I = current

Φ = magnetic flux

Mutual-Inductance

M= N2​Φ21​/ I1​

Where,

M = Mutual Inductance

N = Number of turns

I = Current

Φ21 = flux in coil1 through the coil2

Here are some of the core factors that are responsible for affecting the inductance:

• N (Number of Turns): More turns will lead to higher inductance.
• A (Cross-sectional area): Larger surface area will produce more magnetic flux which will lead to higher inductance.
• L (Length of the coil): Length of the coil is inversely proportional to inductance. More the length, lower will be the inductance.
• Core Material: Ferromagnetic cores can increase the inductance.

Inductance as a property is heavily important for designing of various appliances, which we use in our day to day lives. Here are some core examples which the JEE aspirants need to be familiar with:

• Motors
• Electric Generators
• Transformers
• Inductors in circuits
• Transformers
• Ignition Coils
• Hydro Electric Power Plants
• Wind Turbines