When we consider a point charge q moving with a velocity `vecv` at a given time in presence of magnetic field `vecB`, the charged particle experiences a magnetic force `vecF_m = q[vecv xx vecB]`. The force was first given by H.A. Lorentz and is called the Lorentz magnetic force. The force depends on q, `vecv and vecB` and involves a vector product of `vecv and vecB`. The force acts in a side ways direction perpendicular to both the velocity and magnetic field and the direction is given by right hand thumb rule for vector product. Obviously force on a negative charge is opposite to that on a positive charge.
When will a moving charge experience maximum force due to a magnetic field?

Explanation

The moving charge experiences maximum force `F = q vB` when `vecv` and `vecB` are in mutually perpendicular directions.