Electric and magnetic forces need not be perpendicular at all. For example, magnetic and electric fields can be perpendicular to each other in such a way that the electric and magnetic forces are parallel. One can make them in opposite directions so that they cancel. Such a device is called a spin rotator, or Wien filter. It is in common use; I've designed some myself.DB said:Why is it that as a particle propagates through an electromagnetic field, the electric and magnetic forces are perpendicular to eachother?