(fig. 1-15). These curved lines, extend from the two
poles of the magnet, follow the magnetic lines of force
surrounding the magnet. Lines of force rules are as
The lines of force (outside the magnet) pass from
the North Pole to the South Pole of the magnet.
The lines of force act somewhat as rubber bands
and try to shorten to minimum length.
The lines of force repel each other along their
entire length and try to push each other apart.
The rubber band characteristic opposes the
The lines of force never cross each other.
The magnetic lines of force, taken together, are
referred to as the magnetic field of the magnet.
The magnetic fields of a bar and of a horseshoe
magnet are shown in figure 1-16. In each, note how the
lines of force curve and pass from the North Pole to the
Effects between magnetic poles (fig. 1-17). When
two UNLIKE magnetic poles are brought together,
they attract. But when LIKE magnetic poles are
brought together, they repel. These actions can be
explained in terms of the rubber band and the push-
apart characteristics. When unlike poles are brought
close to each other, the magnetic lines of force pass
from the North Pole to the South Pole. They try to
shorten (like rubber bands) and, therefore, try to pull
the two poles together. On the other hand, if like poles
are brought close to each other, lines of force going in
the same direction are brought near each other.
Because these lines of force attempt to push apart, a
repelling effect results between the like poles.
An electric current (flow of electrons) always
creates a magnetic field. In the wire shown in figure
1-18, current flow causes lines of force to circle the
wire. It is thought that these lines of force result from
the movement of the electrons along the wire. As they
move, the electrons send out the lines of force. When
many electrons move, there are many lines of force
(the magnetic field is strong). Few electrons in motion
means a weak magnetic field or few lines of force.
Electron movement as the basis of magnetism in
bar and horseshoe magnets can be explained by
assuming that the atoms of iron are so lined up in the
magnets that the electrons are circling in the same
direction and their individual magnetic lines of force
add to produce the magnetic field.
The magnetic field is produced by current flowing
in a single loop of wire (fig. 1-19). The magnetic lines
of force circle the wire, but here they must follow the
Figure 1-15.Magnetic lines of force.
Figure 1-16.Bar and horseshoe magnet.