EMF Induction: How Flux Change Creates Potential

[mikeph]

No. Faraday's law covers this whole thread. a dB/dt is accompanied by a curl(E) of the same magnitude and opposite direction. That's it.

 

[Entanglement]

No. Faraday's law covers this whole thread. a dB/dt is accompanied by a -curl(E) of the same magnitude.

How does that varying flux create an electric field ?

 

[jtbell]

How does that varying [magnetic] flux create an electric field ?

How does a charge produce an electric field?

How does a current produce a magnetic field?

All these come out of Maxwell's equations, which are a starting point for classical electromagnetism as Newton's laws of motion are a starting point for classical mechanics.

And there's more! Maxwell realized that the equations as he originally formulated them were mathematically inconsistent, and to resolve that, he proposed adding a new term to one of them, which predicted that:

A varying electric flux creates a magnetic field.

This led him to predict that self-propagating waves of electric and magnetic fields should exist, and that they should travel at a speed which turned out to be equal to the speed of light! (within experimental uncertainties in electromagnetic experiments and in the speed of light)

 

[Drakkith]

I don't think there is an easy answer for this. I believe a full understanding would involve getting into the basic relationships of electric and magnetic fields and how they depend upon frames of references.

 

[Entanglement]

How does a charge produce an electric field?
How does a current produce a magnetic field?
All these come out of Maxwell's equations, which are a starting point for classical electromagnetism as Newton's laws of motion are a starting point for classical mechanics.

Maxwell's equations are way more difficult than my level, I was just seeking for a basic explanation.

 

[jtbell]

Maxwell's equations are the basic explanation. Sorry.

 

[Entanglement]

Maxwell's equations are the basic explanation. Sorry.

I understand how an emf is induced when a wire cuts magnetic flux lines.
The motion of the electrons with the wire induces a magnetic field which interferes with external magnetic field so the electrons are forced to move along the wire, leading to the accumulation of the electrons at one end of the wire, creating a potential difference. I thought that induction in coils should be somehow similar to induction in a wire cutting flux lines.

 

[nsaspook]

I thought that induction in coils should be somehow similar to induction in a wire cutting flux lines.

Two phenomena

http://en.wikipedia.org/wiki/Faraday's_law_of_induction#Faraday.27s_law_and_relativity
http://en.wikipedia.org/wiki/Relativistic_electromagnetism

 

[sathwik]

But isn't Bvq the main reason for induction ??

Bvq is also a reason for induction
There is also other case where the emf is induced due to rate of change of area

 

[rude man]

Maxwell's equations apply to all stationary e-m phenomena, including how a change in B generates an emf. They are based on EXPERIMENTAL EVIDENCE and must be accepted. There is no other way to explain induction in non-moving media.

Bvq is the magnetic force on a charge in motion. The emf = Blv law stems directly from that. (Simplified, E = emf/l = F/q = qvB/q so emf = Blv).

Maxwell's equation on which stationary-media emf generation is based is ∇xE = -∂B/∂t.
But for moving media this has to be expanded to ∇xE = ∇x(vxB) - ∂B/∂t. The Blv term comes from the first term on the right.

I know you don't have the math background to understand these equations but you should at least be able to appreciate the fact that there are two separate induction mechanisms for generating an emf.

 

[sathwik]

Can anyone explain me about divergence theorem