# Magnetism, Helixes

1. Jan 14, 2006

### runicle

The coil wrapped around a magnet is attached to a battery (one end of the coiled attached the positive end of the battery and same goes to the negative side). I am confused with the right hand rule. Your thumb is to point to North, but North is what? The positive side of the battery? As you know I'm confused and not really sure if I'm making sense.

2. Jan 14, 2006

### Staff: Mentor

There are a bunch of right-hand rules, each of which is generally and confusingly called "the right-hand rule". The one that you are probably refering to is that if your fingers curl in the direction of the current in a loop then your thumb points in the north direction of the magnetic field produced at the axis of the loop. Remember that current always flows from the + terminal to the - terminal.

So, imagine following the current from the + terminal to your loop. Is the current then going clockwise through the loop or counter-clockwise. Make your fingers curl in that same direction and then your thumb will show you which direction is the north side of the resulting field.

-Dale

Last edited: Jan 14, 2006
3. Jan 14, 2006

### lightgrav

The more generally applicable right-hand rule for production of B-field is
to grab the wire with your thumb in the direction of (Indicated) electric current.
Your fingers encircle the wire the same way as the B-field encircles I.
Note: the B_vector outside the helix is opposite the B_vector inside it.

4. Jan 15, 2006

### runicle

Okay, how would i find the current when i'm given the north of the magnet and find the north if i have the current.