The magnetic force on a charge q, moving with velocity v in a magnetic field B is given by

`vecF = q(vecv xx vecB)`

This is known as the Lorentz force law. If electric and magnetic both field are present the net force on q would be `q[vecE + (vecv xx vecB)]`

magnitude of magnetic force is given by `F = qvB sintheta`


`text(Direction)`

Force is perpendicular to both velocity and magnetic field. Its direction is same as `vecv xx vecB` if q is positive and opposite of `vecvxxvecB ` if q is negative.

Case 1: If q = 0, then F = 0 , neutral particles do not experience magnetic force.

Case 2: If v = 0, then F = 0 , stationary charges do not experience magnetic force.

Case 3: If `theta = 0 or pi `, then F = 0 i.e., when a charge moves parallel or ami-parallel to magnetic field it does not experience magnetic force.

Case 4: If `theta = pi/2` then `F = qvB` is maximum. If R is uniform the particle will trace a circular path, if r is the radius of the path then for circular motion.

`(mv^2)/r = qvB`