# Homework Help: Emf induced by a changing flux

1. Sep 7, 2008

### learning_phys

$$\xi = - \frac{dB}{dt}$$

Is the emf induced by a changing flux. Is the current created by this emf conventional current?

For example. Say there is a square loop in the plane of this page, with a decreasing magnetic field going INTO this page. This creates a clockwise current to battle the change in B. Now say there was a voltage supply attached to this loop so it looks like this:

|----------|
| x x x x x |
| x x x x x |
|---l |-----|
-V+

The voltage V gives a conventional current to go clockwise. Would the current introduced by scenario above add do this voltage or subtract?

I guess my question is, is the clockwise current induced by the decreasing magnetic field a conventional current?

2. Sep 7, 2008

### granpa

Re: flux

think about it this way, there is energy stored in the magnetic field and that energy has to go somewhere.

3. Sep 11, 2008

### learning_phys

Re: flux

and that does not help at all, gran(d)pa

4. Sep 11, 2008

### granpa

Re: flux

how do you suppose that transformers work?

5. Sep 11, 2008

### LowlyPion

Re: flux

Yes.
Actually it's voltage by Faraday's Law of Induction. If there is an impedance for it to operate on then current flows.
By the right hand rule the current would be clockwise as well.
Yes. It's a conductor. Presumably it has impedence somewhere in the circuit.