Principles of Motor Application
A magnetic filed forms between unlike poles, and a current-carrying conductor produces a magnetic filed around it. In the magnetic field between unlike poles, the direction of flux is always from north to south. In a current-carrying conductor, the direction of flux depends on the direction of current in the conductor (left hand rule for conductors)
When a current-carrying conductor is placed in the magnetic field between unlike poles, the magnetic fields interact and cause the conductor to move. On the side of the conductor where the direction of flux of both magnetic fields is the same, the lines of force are crowded together, strengthening the field on this side of the conductor and weakening it on the other. Because they are crowded together and distorted, the lines of force on the side with the strong magnetic field tend to push the conductor toward the rare side.
However, these lines of force are distorted because they are the flux from both magnetic fields crowded together. To realize how they force the conductor upward, imagine them as elastic bands, which having been stretched out of shape, will tend to straighten and spring back in the opposite direction.
With current in the conductor flowing away the magnetic flux around it is in the opposite direction, and the conductor is forced downward. The operation of an electric motor depends on that fundamental principle- that a conductor carrying a current in a magnetic field tends to move at right angles to that field.
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