Current is the flow of charge. The size of the current is the rate of flow of charge. A moving charged particle can be considered to be a current.If a charged particle with charge Q moves at speed v through a uniform magnetic field and moves at right angles to the field, it will experience a force at right angles to the field and at right angles to its direction of motion v according to the motor effect. Since the force is always at right angles to the direction of motion, the force will provide a centripetal force F = BQv, and the charged particle will follow a circular path.