Motion in a Magnetic Field

By the "motion" of a magnetic field line, we mean that path in time that is traced out by low energy test electric charges that are initially spread along the field line. The test charges move because they drift in the electric field arising because of the time-changing magnetic field. As time progresses, the test charges move with the "field line" as we have defined it--that is we use the low energy test charge motion todefine the concept of field line motion.

Thus the motion we show in our computer visualizations has a physical basis--it is the motion we would observe for low energy test charges initially spread along the various magnetic field lines as the situation evolves in time.

A magnet is an object that has a magnetic force. Magnetic force exists around a magnet or electrical field. An electric field is a space surrounding an electric charge. We can say, therefore, that magnetic force is generated electromagnetically.This is a familiar concept in space plasma physics.