# Determine the direction of the magnetic field

1. Mar 10, 2005

### Haftred

If I were to put a coil of wire in and out of a magnetic field, how can I determine which way the current will go (clockwise or counterclockwise)?

Last edited by a moderator: Jul 15, 2014
2. Mar 10, 2005

### erik05

I think the easiest way is to use one of the hand rules depending if the current is conventional (right hand) or electron (left hand).
It would probably help too if you knew the direction of the magnetic field (ie. going into or out of the page).

3. Mar 11, 2005

### Galileo

If you know the direction of the magnetic field, you can also use Lenz' law:
The induced current is such as to oppose the change in flux.
So if the flux through the coil increases, current will flow in a way as if to cancel the change in the magnetic field.

4. Mar 11, 2005

### Chi Meson

To expand on Galileo's comment

1: determine the direction of the magnetic field
2: determine whether the field is increasing or decreasing in the coil
3: use 1 & 2 to determine direction of change in flux *
4: induced current creates a magnetic field that opposes the direction found in 3

*Say the field is pointing out of the page, and is increasing; change in flux is out.
The field is pointing out of the page and is decreasing; change in flux is into page
Field points into page and is decreasing; change in flux is out of page. Etc etc.