Page 470 - Basic Electrical Engineering

material which contain iron, nickel, and cobalt.
Permanent magnets are made of material like alnico (alloy of aluminium,
nickel, and cobalt) in which the magnetism once created is retained for a very

long time, i.e., the magnetic property is permanently set. Electromagnets are
made by placing a coil around a magnetic material which forms the core.

They demonstrate magnetic properties as long as current flows through the
coil.

Magnetic field is the area around a magnet in which there is influence of
the magnet. This can be tested by bringing a magnetic needle near a magnet

and observing the deflection of the needle. The magnetic field around a
magnet is shown through lines of force. There are very large number of lines
of force around a magnet. Lines of force are closed curves. The lines of force

come out of the magnet body from the North pole and enter the South pole
and close their path through the magnet body. The pattern of lines of force is

the same for a permanent magnet and for an electromagnet. Fig. 5.1 shows
magnets and magnetic fields of permanent magnets and electromagnets of

different shapes.