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# how does a changing flux density induce an emf watch

1. basically what the thread title says.
2. Faraday's law: "the magnitude of the induced EMF is equal to the rate at which magnetic flux is cut"... since a moving charge produces a current, a current produces a magnetic field. This magnetic field has a magnitude know as the magnetic flux density.
so... if you move a charge through a magnetic field, a current will be produced which is proportional to the charge and the strength of the magnetic field.
F=BQV maybe? where F would be the force on the charge (causing the electron to move and produce a current?).

3. so... if you move a charge through a magnetic field, a current will be producedwhich is proportional to the charge and the strength of the magnetic field.
Well, if you move a charge, you already have current. Current is produced when charge starts to move as a result of electromotive force which is a result of changing magnetic field.

F=BQV maybe? where F would be the force on the charge (causing the electron to move and produce a current?).
The formula is not to useful here, and the second part of the statement is incorrect. Magnetic force will act on the charge only if the particle is already moving; moreover, magnetic field never accelerates particles but only changes the direction of movement. Therefore, magnetic force is never the source of current.

What makes charge move is electric force. Electric field is produced as a result of changing magnetic field. It's electric field that accelerates charged particles.

If you want a quantitative expression, Maxwell's equations come in helpful:

.
4. What makes charge move is electric force. Electric field is produced as a result of changing magnetic field. It's electric field that accelerates charged particles.
Cheers. That is a little gem.
5. (Original post by jaroc)
Well, if you move a charge, you already have current. Current is produced when charge starts to move as a result of electromotive force which is a result of changing magnetic field.

The formula is not to useful here, and the second part of the statement is incorrect. Magnetic force will act on the charge only if the particle is already moving; moreover, magnetic field never accelerates particles but only changes the direction of movement. Therefore, magnetic force is never the source of current.

What makes charge move is electric force. Electric field is produced as a result of changing magnetic field. It's electric field that accelerates charged particles.

If you want a quantitative expression, Maxwell's equations come in helpful:

.
Thanks for correcting me

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