These units measure "quantity of magnetism", also known as magnetic pole strength, which is the phenomenon of electrical charge in motion with fixed velocity. This appears to be the ultimate cause of magnetic forces. It can be viewed as the effect of observing the forces produced by electric charge, but observed from a moving reference frame, as a consequence of Einstein's Special Theory of Relativity. This quantity is often symbolized
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| body | \mathbf{q}_m = q \mathbf{v} |
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, where
is electric charge and
is velocity.
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