# Right hand rule confusion

1. Oct 8, 2011

### pyroknife

for the right hand rule for a wire with a current and magnetic field. Your thumb points in the direction of the current and you wrap your fingers around the wire. Do your fingers form a fist or how much do you curl it? Right now, I'm curling my fingers where the tips of my fingers TOUCH my palm and that gets me the right answers. Is that how it's down?

2. Oct 8, 2011

### robphy

The point of grabbing the wire with your right-hand is to indicate
the sense of the magnetic field...

Specifically, a given point in space,
the magnetic field due to a long straight wire is
pointing tangent to a circle through your point and centered at the wire.
Which way along the circle (clockwise or counterclockwise)?
The way your right hand grabs the wire (with thumb along the positive current) indicates which way.
(It doesn't matter how much you curl it... The point is that your right hand can only curl in one direction.)

3. Oct 8, 2011

### pyroknife

yeah but how much do you curl your finger? All the way?

4. Oct 8, 2011

### Ray Vickson

It doesn't matter. Curl them all the way if you want; don't curl them at all if you prefer. The answer is still the same: you get the ORIENTATION of the magnetic field, not necessarily the detailed direction.

RGV

5. Oct 8, 2011

### pyroknife

a problem that I had to do dealt with a wire. The problem was that a wire is located at y=6m that is 2m long and the current is flowing towards the +x direction. It wanted to know whether the magnetic field was +/- at x=0. I had to curl my hand all the way to get that it was positive.