How To Use the Right Hand Rule to Find the
Direction of Magnetic Force
This Right Hand Rule relates magnetic force ~
FB, magnetic
field ~
Band velocity ~v of a moving charge (equivalently, current,
since current is just moving charge.)
There are at least three ways to apply the Right Hand Rule.
You can use whichever one you like best, or even make one up.
But I suggest that you pick one way and stick to it to avoid
getting confused.
1. “Finger curling way”: First draw (or imagine) the vec-
tors. Align your fingers along vector ~v (the first one in
the cross product). Arrange your hand in such a way that
your fingers can curl naturally around to vector ~
B. Then
your thumb points in the direction of the cross product (the
magnetic force in our case).
Here’s a link I found where this curling action is animated:
http://www.phy.syr.edu/courses/video/RightHandRule/rhr-1-1m.gif
2. “Finger pointing way”: Align your index finger along ~v
and your third finger along ~
B. Then your thumb points in
the direction of the cross-product ~
FB.
3. “Palm way”: Point your thumb in the direction of ~v, your
fingers in the direction of ~
B, and your palm points in the
direction of the cross-product.
Don’t forget the RHR gives the direction for a positive par-
ticle, and that if qis negative the force is in the opposite
direction!
