Electromagnetism Electromagnetism

Figure 5 The arrangement of domains in an
object determines whether the object is magnetic.
If the domains in an object are randomly
arranged, the magnetic fields of the individual
domains cancel each other out, and the object
overall has no magnetic properties.
Losing Alignment The domains of a magnet may not always
stay aligned. Dropping a magnet or striking it too hard can
jostle the domains out of alignment, causing the magnet to
lose its magnetic properties. Increasing the temperature of a
magnet can also demagnetize it. At higher temperatures, atoms
in the magnet vibrate faster and lose their alignment within
the domains.
Making Magnets A magnet can be made from an unmagnetized
object made of iron, cobalt, or nickel by aligning the
domains in the object. For example, you can magnetize an
iron nail if you rub it in one direction with one pole of a magnet.
The magnetic field of the magnet will cause the domains
in the nail to rotate and align with the domains in the magnet.
As more domains become aligned, the overall magnetic
field of the nail will strengthen, and the nail will become
a magnet, as shown in Figure 6.
The process of making a magnet also explains how a
magnet can pick up an unmagnetized object, such as a
paper clip. When you hold a magnet close to a paper clip,
the magnetic field of the magnet causes the domains in
the paper clip to align slightly, creating a temporary
magnet. The domains align such that the north pole of
the paper clip points toward the south pole of the magnet.
The paper clip is therefore attracted to the magnet.
The domains of the paper clip return to a random
arrangement after the magnet is removed.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
If most of the domains in an object are
aligned, the magnetic fields of the individual
domains combine to make the whole
object magnetic.
Figure 6 This nail was
magnetized by rubbing
it with a magnet.
Electromagnetism 457