It is equal to a force on a point charge due to electromagnetic fields.
It is given by the following equation in terms of electromagnetic fields:
F = q [E + (v x B)]
F = force (in newtons)
E = electric field (in volts per meter)
B= magnetic field (in teslas)
q = electric charge of the particle (in coulombs)
v = instantaneous velocity of the particle (in meters per second)