Learning objectives By the end of this chapter, you should be able to:
list the properties of magnets identify materials capable of exerting a magnetic field
describe the effects of magnetism on other materials
demonstrate magnetic field lines
describe the magnetic effects of different current-carrying conductors
use the right-hand grip rule to determine the magnetic field direction in a current-carrying conductor
list the uses of magnets in geography and in industry.
CHAPTER 26 MAGNETISM
Properties of magnets Magnets have a number of important properties.
• Magnets attract ferromagnetic materials (such as nickel, cobalt, steel and iron). • They cause temporary magnetism in the ferromagnetic material when they are near or in contact with it. When a magnet is placed in contact with ferromagnetic materials such as paper clips, each paper clip gains some temporary magnetism and attracts another clip (Fig. 26.1a).
• When freely suspended, magnets will line up roughly north–south. • Like poles will repel and unlike poles will attract (Fig. 26.1b).
The laws of light and of heat translate each other; so do the laws of sound and colour; and so galvanism, electricity and magnetism are varied forms of this self-same energy.
– Ralph Waldo Emerson
FIG. 26.1a A magnet causes temporary magnetism in ferromagnetic material such as paper clips
FIG. 26.1b Like poles repel and unlike poles attract
Magnets or lodestones were first widely used in Magnetia, a province in Asia. They exert a magnetic field on certain objects.
