# Induced emf in a loop

1. Apr 9, 2005

### Giuseppe

Hey, I'm in a high school AP class and am stuck! Can anyone help me with this problem concerning induced emf? I would surely appreciate it.

There is a loop of wire, shaped like a square. Each side is 20 cm long.
There is a magnetic field directed into the page.

What would be the way of finding out what the induced emf in the loop. The back of the book says that the answer is 1.40 x 10^-4 Volts.

2. Apr 9, 2005

### marlon

Well, how is an induced current 'created'. I mean, what will you need to do, so that a current is generated in the loop ??? What will have to change ???

regards
marlon

ps : LENZ'S LAW (or more generally, the Faraday induction law)is the direction you are looking for.

3. Apr 9, 2005

### Andrew Mason

You are missing some important information such as the magnitude of the field and either its rate of change or the motion of the loop.

The induced emf is given by Faraday's law:

$$V_{induced} = \frac{d\phi}{dt}$$

In this case, the flux is BA where A is the area of the square loop. How does this change with time?

AM