Faraday's Law Paradox (1 Viewer)

[QZP]

I was doing some questions and picked up on a neat paradox (had to talk to physicist teacher to explain this one ).

Suppose you have a rotating metal disc fully immersed in a uniform magnetic field as such:


Try to predict what happens, and explain it if you can. P.S google is cheating

 

[anomalousdecay]

Not exactly a paradox

 

[someth1ng]

It's called Faraday's disc

 

[QZP]

Ah, well there's an article on wiki called Faraday Paradox on exactly this

 

[anomalousdecay]

Its wiki lol.

I'm sure "disc" is much more appropriate than "paradox", though I guess they both comply.

 

[hit patel]

Interesting.

 

[theodore0307]

It slows down. That's how em braking works.

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[QZP]

It slows down. That's how em braking works.

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Not quite. EM braking relies on the metal disc experiencing a changing magnetic flux (achieved through either only a portion of the disc immersed in a magnetic field, or a changing magnetic field provided by electromagnets).
In the above setup, it is not (since disc entirely immersed in constant magnetic field).

 

[xGhanem]

Not quite. EM braking relies on the metal disc experiencing a changing magnetic flux (achieved through either only a portion of the disc immersed in a magnetic field, or a changing magnetic field provided by electromagnets).
In the above setup, it is not (since disc entirely immersed in constant magnetic field).

Doesn't the spinning of the disk cause a change in magnetic flux?

 

[QZP]

Doesn't the spinning of the disk cause a change in magnetic flux?

You're right, but think about this. As the disc rotates, the amount of magnetic flux threading any area on the disc is not changing.

 

[hit patel]

Maybe the electrons experience a force therefore probably cause a current? And maybe it has something to do with the geometrical properties of a circle and therefore can cause like angular velocity for electrons?