The right hand rule for magnetic force

The right-hand rule for magnetic force

A charged particle moving through a region of magnetic field experiences a magnetic force. This force is directed perpendicular to both the velocity vector and the magnetic field vector at the point of interaction. The requirement that the force be perpendicular to both of the other vectors specifies the direction of the force to within an algebraic sign. This algebraic sign is determined by the right-hand rule. To employ the right-hand rule:

1. Spread your right thumb and index finger apart by 90 degrees.
2. Bend your middle finger so that it is perpendicular to your thumb and index finger.
3. Orient your hand so that your thumb points in the direction of the velocity and your index finger in the direction of the magnetic field.

If the charge is positive, your middle finger is now pointing in the direction of the force as shown.

If the charge is negative, the force is in the direction opposite your middle finger.