# What is the purpose of an inductor?

If an inductor requires a changing current to produce a voltage drop across itself Then is there any purpose to an inductor with constant current going through it? Is AC usually used with inductors since its always changing.

NascentOxygen
Staff Emeritus
If an inductor requires a changing current to produce a voltage drop across itself Then is there any purpose to an inductor with constant current going through it? Is AC usually used with inductors since its always changing.
Inductors come in all shapes and sizes. They have various uses, many at the fundamental level basically exploit the inductor's mathematical function that ##v(t)\ =\ L.\dfrac{di(t)}{dt}##
though some applications also exploit non-linear behavior of the inductor's core material.

Where the inductor current is fixed, often it's the presence of the inductor that is causing the circuit current to be constant.

An example where an inductor may be fed a constant current is an electromagnet.

AchillesWrathfulLove
Here is another question about Inductors. What kind of energy is stored in inductors? Capacitor is easy because it is stored in an electric field and that is basically just more electrons on what side of a "plate" than the other which is potential energy in the classical mechanics sense. What about an inductor, is that potential energy, if so how so?

anorlunda
Staff Emeritus
Magnetic field. To the uninformed, electric fields sound more "physical" than magnetic fields, but in reality they are both part of the same electromagnetic effects.

Fisherman199
I always found thinking of electromagnetism as oscillating charges as opposed to oscillating electromagnetic fields. Something more physical to grasp as an idea I suppose.

anorlunda
Staff Emeritus
I always found thinking of electromagnetism as oscillating charges as opposed to oscillating electromagnetic fields. Something more physical to grasp as an idea I suppose.

That is a really poor way to learn things, just sitting there trying to visualize them in your mind. I suggest a textbook, or a course on video as much more effective ways to learn.

Fisherman199, Asymptotic, sophiecentaur and 2 others

jim hardy
Gold Member
Dearly Missed
I always found thinking of electromagnetism as oscillating charges

The way to appreciate inductance is working with it -

Sadly automobiles no longer have points .
Every kid in my generation got 'bit' by the inductive 'kick' of an ignition coil;
which gives you a literal feeling of e = -L di/dt . (or if you prefer Δamps / Δtime) .

https://www.instructables.com/id/Simple-Experiment-to-Visualize-Magnetic-Fields/

sophiecentaur and NascentOxygen
jim hardy
Gold Member
Dearly Missed
I always found thinking of electromagnetism as oscillating charges as opposed to oscillating electromagnetic fields. Something more physical to grasp as an idea I suppose.

Think of magnetic flux as a massless fluid that surrounds any current.
We can't see it, i guess Mother Nature wanted us to figure it out when we were ready.
But the old "Sprinkle iron filings around a coil with DC" trick reveals it
picture courtesy of https://physics.unm.edu/pandaweb/demos/images/5h1540.jpg

you can even see the little circles surrounding each individual wire . In a transformer they'd be 'leakage flux.

With AC current the whole field expands, contracts and reverses direction at line frequency..