Magnetic force is the same as gravitational and electrical forces in that no one knows truly what it is. Magnetic force is different from gravitational and electrical forces in that its potential and momentic energy is at the expense of an electrical field in time.
The existence of a magnetic field is a necessary consequence of the laws of electrostatics, and the principles of special relativity. One of the prerequisites of special relativity is there must be motion, and it is in effect when the observer is in motion relative to the system from the observer's point of view.
|The classical development of
magnetics started when Oersted deflected a compass needle with a electric
current carrying wire. Thus, it became believed, all so called magnetic
phenomena result from forces between electric charges in motion. The
charges in motion relative to an observer set up a magnetic field and an
electric field which exerts canceling forces on the second charge relative
to the observer.
Because it is very easy to move charges through an wire, most all knowledge about magnetics comes from the study of a current through a wire. However, this is the same as the movement of small electric fields through the wire.
In the early development of magnetic theory, bar magnetics were used to provide a fixed magnetic source. The magnetic field in a bar magnetic had two definite poles. For the lack of any thing better, early scientists referred to these poles as north and south. More modern terminology is positive and negative. One thing that is agreed upon is that there is two distinct opposite in characteristic poles.
It was found fairly simply that a force is developed between two bar magnetics. When the poles are alike; N-N or S-S, the force is repelling. When the poles are opposite; N-S or S-N, the force is attracting.
F force direction is directly relative to q's polarity with respect to two charges.
General experiments using proton and electron beams in a vacuum perpendicular to a magnetic field, show the direction of deflection of a positively charged particle and a negatively charged particle are 180 degrees from each other