If a charged particle is at rest, external magnetic field cannot move it. If an external electric field is applied, the particle will get accelerated. Now the external magnetic field will exert a force on the particle perpendicular to its motion. This will change the direction of motion of the particle. However, in magnetostatics, there is a frequent use of uniform motion of charge particle. Is this "uniform motion" just a hypothetical postulate to formulate the theories or such a motion can really be created? If a charged particle can really move in uniform linear motion it seems very interesting to know about the forces acting on the particle and how the forces are balanced.