# Inductor behavuiour ..

Discussion in 'Physics' started by RRITESH KAKKAR, Dec 31, 2013.

1. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
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Hi,

When current start decaying/discharging in inductor it induce back EMF of "opposite polarity" and induce voltages spikes across it...by mathematical expression it is proved reason by what is the actual or practical reason behind it?

2. ### MaxHeadRoom Expert

Jul 18, 2013
10,851
2,522
Collapsing field inducing current in the winding.
Max.

3. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
The natural laws governing electromagnetics. Namely, a current produces a magnetic field, a changing current produces a changing magnetic field, a changing magnetic field produces a voltage.

Now, you can certainly delve deeping into the quantum electrodynamics, but hopefully this will suffice.

4. ### amilton542 Active Member

Nov 13, 2010
494
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There is no such thing as a pure mathematical reasoned proof for any part of physics. This is where the two diverge; namely applied math.

The maths is in agreement with the data of best fit.

Side-note:

I'm always at odds why project builders whom by consider themselves notorious still conceive difficulty in picking up a textbook to seek such basic principles?

5. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Joule Thieves do a pretty good job of demonstrating theory though. A voltage boost with nothing but a oscillator and an inductor.

6. ### amilton542 Active Member

Nov 13, 2010
494
64
Hmmm, your signature disagrees.

Mar 24, 2008
20,772
2,540
Huh?......

8. ### cirkuit New Member

Jan 16, 2014
3
1
I think he means your "Good enough is enemy of the best".

And for the inductor question, the math behind it is that Voltage= Inductance* di/dt.
As the current decreases it creates a voltage in the opposite direction. The "practical reason" behind it would be if you see it this way: Capacitors store energy as a charge separation or electric field and inductors store energy in a magnetic field.

As the current decreases, the energy gets released back in the circuit in the form of a back emf.

Please do correct me if I'm wrong, I'm really sleepy.

9. ### russ_hensel Distinguished Member

Jan 11, 2009
820
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The fundamental classical answer is "Maxwell's Equations". These are in reach of a first or second year college physics course. These are pretty good equations, consistent with special relativity, but need adjustment for quantum mechanics.