Magnetism

The principles of magnetism play an important role in the
operation of an AC motor. All magnets have two characteristics.
They attract and hold metal objects like steel and iron. If free
to move, like the compass needle, the magnet will assume
roughly a north-south position.

Magnetic Lines of Flux

We know that a magnet attracts an iron or steel object by an
invisible force. The magnet’s invisible force is called lines of flux.
These lines of flux make up an invisible magnetic field. Every
magnet has two poles, one north pole and one south pole.
Invisible magnetic lines of flux leave the north pole and enter
the south pole. While the lines of flux are invisible, the effects
of magnetic fields can be made visible. When a sheet of paper
is placed on a magnet and iron filings loosely scattered over it,
the filings will arrange themselves along the invisible lines of
flux

By drawing lines the way the iron filings have arranged
themselves, the following illustration is obtained. Magnetic lines
of flux always form closed loops, leaving the north pole and
entering the south pole. They return to the north pole through
the magnet

                               Unlike Poles Attract

                      Like Poles Repel