How To Use the Right Hand Rule to Find
the Direction of Magnetic Force

This Right Hand Rule relates magnetic force $\vec{F}_B$, magnetic field $\vec{B}$ and velocity $\vec{v}$ of a moving charge (equivalently, current, since current is just moving charge.) Essentially, the RHR gives the direction of the vector cross-product $\vec{F}_B= q\vec{v} \times \vec{B}$.

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 vectors. Align your fingers along vector $\vec{v}$ (the first one in the cross product). Arrange your hand in such a way that your fingers can curl naturally around to vector $\vec{B}$. 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.perry-lake.k12.oh.us/phs/Classdept/sciencedept/
   physics/tutorials/e_m/mag1/rhr.htm

2. ``Finger pointing way'': Align your index finger along $\vec{v}$ and your third finger along $\vec{B}$. Then your thumb points in the direction of the cross-product $\vec{F}_B$.

   Figure 1: The ``finger pointing way''.

   

3. ``Palm way'': Point your thumb in the direction of $\vec{v}$, your fingers in the direction of $\vec{B}$, and your palm points in the direction of the cross-product.

   Figure 2: The ``palm way''.

   

Don't forget the RHR gives the direction for a positive particle, and that if $q$ is negative the force is in the opposite direction!

Of course, you can use the RHR ``backwards'', if you know the force and you need to find one of the other quantities.