# Homework Help: Final review

1. May 5, 2005

### waywardtigerlily

Hello.
I am studying for my final and I can't remember how to find the induced magnetic field. I need it because, in my right hand rules handout that i must know, it says put your thumb in the direction of the induced magnetic field and you will curl your fingers into the direction of the induced current.
Thanks!

2. May 6, 2005

### whozum

Its backwards, your thumb points the direction of the current, and yor fingers curl in the direction of the magnetic field.

3. May 6, 2005

### ZapperZ

Staff Emeritus
No no no!

You point your thumb along the "thingy" that is in a straight line. This could be either the current, or the magnetic field! I will demonstrate two examples.

1. You have a straight wire with a current in one direction. Here, you use your thumb to point in the direction of the current, and the curl of your fingers will tell you the circular direction of the current.

2. You have a loop of wire that has a current in one direction. Here, you curl your fingers in the direction of the current, and the direction that your thumb is pointing is the direction of the magnetic field.

Induced magnetic field has an added complexity because you have to apply Lenz's Law to the situation. Unless you have a specific problem you're working with, it's tedious to explain how to use the right-hand rule in general.

Zz.