# Understanding Inductors

Discussion in 'General Electronics Discussion' started by Cham, Aug 15, 2015.

1. ### Cham

18
0
Aug 11, 2015
I've been studying inductors and their use in L/C resonance circuits, but I don't like using components that I don't fully understand. I get that inductors resist change in current, but I don't understand how or why. I also don't completely understand their purpose in the L/C resonance circuit. Any help on the matter would be greatly appreciated!

2. ### davennModerator

13,833
1,950
Sep 5, 2009
hi there

what research have you done so far on inductors ?
there's lots of info out there
of you have read something specific somewhere and don't quite understand it
post a link to that site and comment on the part you don't understand, then someone can help you

Dave

3. ### Cham

18
0
Aug 11, 2015
Hi, sorry for the late response!

Yeah, there's a ton of stuff out there, all hard to visualize between the magnetic fields and whatnot. Not to mention, I'm still getting started. I was just checking out the wikipedia page for inductors: https://en.wikipedia.org/wiki/Inductor and the page for lc circuits: https://en.wikipedia.org/wiki/LC_circuit. The animation in the LC page was the most helpful, but it didn't quite click for me yet. I'm sure I could learn a lot about inductors by learning how they work in the LC circuit.

4. ### Minder

3,092
661
Apr 24, 2015
Remember that the current leads the voltage in a capacitor, and voltage leads the current in a inductor.
When a alternating current is applied to an inductor the positive going waveform creates a magnetic field in a certain direction or polarity, upon reversal of the negative going part of the waveform the now collapsing previous field is opposing the attempt to create a field of the opposing polarity.
So something called inductive reactance is created and is measured in Ohms.
This value is essentially in series with the DC resistance of the coil.
The animation of the parallel tuned circuit shows the energy stored in the tuned circuit oscillating, the capacitors charge flows into the inductor after which the inductor energy flows back into the capacitor because of the phase difference at resonance.
Resonance is when the capacitive reactance equals the inductive reactance at the applied frequency, (the energy swings back and forth).
M.

davenn likes this.
5. ### Colin Mitchell

1,417
313
Aug 31, 2014
I have described inductors in a completely different way on my website but I am not allowed to give the link as I get banned from the forum for promoting my website.
The most important part to understanding an inductor is the fact that it produces magnetic flux when a current flows and this flux cuts all the the other turns of the coil and produces a voltage in all these turns that is OPPOSITE the applied voltage.
This means the applied voltage may be 12v and the "back voltage"produced by the inductor may be 11.5v.
That means the net forward voltage is only 0.5v and that's why very little current will be flowing.
The other interesting feature of an inductor is this: When you turn off the voltage, the magnetic flux that was produced (when the voltage was applied), will collapse and produce a voltage IN THE OPPOSITE DIRECTION. This voltage can be MUCH HIGHER than the applied voltage.

hevans1944 likes this.
6. ### BobK

7,682
1,688
Jan 5, 2010
The mathematical equation for an inductor is very simple and easy to understand.

dI/dT = V/L

In English the rate of change of current in the inductor is equal to the voltage across it divided by its inductance.

So, if you apply 1V across a 1 Henry inductor, the current will increase by 1 Amp per second.

Bob

7. ### hevans1944Hop - AC8NS

4,616
2,156
Jun 21, 2012
It is a very interesting and informative website indeed. For anyone interested, Google is your friend if you search for "Colin Mitchell electronics". For lots more on the wonders of inductance, resonance, and other amazing aspects of all things electrical, research (Google) Nikola Tesla whose pioneering inventions electrified the world, although perhaps not exactly has he envisioned it. Colin was not a contemporary of Nikola, but he has been around awhile and knows a thing or three too.

LC resonance reminds me of a Slinky toy when you hold both ends in the palm of your hands and move them up and down in opposite directions. The ripple of the Slinky coils back and forth is NOT analogous to what is going on with an LC circuit, but the exchange of energy back and forth between your two palms is. Same thing happens between an inductor and a capacitor at resonance: the energy sloshes back and forth between the two at resonance. Resonance is a very powerful concept; it has caused the catastrophic destruction of large bridges. Google that!

8. ### Cham

18
0
Aug 11, 2015
I can feel the amount of knowledge this forum is giving me and it's awesome. Thanks a lot, everyone! You've given me a lot to work with. I will be studying this vigorously.