# What is inductance? i need a physical meaning and not equations!

1. Mar 16, 2010

### hisham.i

what is inductance?...i need a physical meaning and not equations!

2. Mar 16, 2010

### collinsmark

Re: inductance

There's more than one way to think about inductance. Here is one such way, as applied to an inductor in a circuit.

Inductors tend to resist change in current. It takes work to get current flowing through an inductor in the first place. Once current is flowing through an inductor, the inductor tends to keep that same amount of current flowing through itself.

The emf (aka Voltage) across the terminals of an inductor are a result of this. The inductor produces an emf in such a way that the overall circuit tends to resist any change in current flowing through the inductor.

I know you didn't want any equations, but I'm going to give you one anyway. The induced Voltage, emf, across an inductor is:

$$V_{emf} = L \frac{di}{dt}$$

where L is the inductor's inductance, and di/dt is the rate of change of current.

So the magnitude of which a component resists change in current is called its inductance.

As a mechanical analogy, think of Newton's laws. An object in motion tends to stay in motion, unless acted upon by an outside force. The amount which a body tends to resist changes in motion is proportional to its mass. Inductors do the same thing, except replace motion with current. The amount that it resists changes in current is proportional to its inductance.

(btw., mutual inductance adds a whole different dimension to this picture, and is a property essential to transformers, power supplies, etc. But I'll leave that for another day.)

3. Mar 16, 2010

### Bob S

Re: inductance

Here is a physics explanation. In an inductor there is a magnetic field. The magnetic field is proportional to the inductor current. The magnetic field represents stored energy. The amount of stored magnetic energy is proportional to the square of the magnetic field** times its volume. The magnetic field (energy) can be in air, ferrite, laminated iron, etc.

** divided by the permeability of the material.

Bob S