A magnet can cause electric currents in conductors. If a bar magnet is moved back and forth inside a coil of wire, an electric current is produced in the wire
MAGNETIC FIELDS
What are magnetic lines of force?
What is the typical pattern fanned by iron filings when two magnets attract each other?
Repel each other?
What are some ways of producing magnetism, in an iron object?
What idea is used to explain some properties of magnets?
Fields and lines of force
There are many ways to study magnetism. One way is to use iron filings. Suppose you place a sheet of glass on top of a bar magnet. Then you sprinkle iron filings on top of the glass. What happens?
If you do this, the first thing you might notice is that the magnet attracts the filings, even through the glass. You might also notice that the iron filings line up in a certain pattern on the glass. By tapping the glass, the pattern becomes clearer. See Figure 17-4.
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You can see only the pattern that is on the glass. But iron filings would be affected in the space all around the magnet. The space in which the iron filings would· be affected is known as the magnetic field of the magnet.
Every magnet has a magnetic field around it. The magnetic field is the area in which magnetic effects are noticeable.
In order to describe a magnetic field, lines are often drawn. The lines are called magnetic lines of force. These lines are a kind of picture of the magnetic field. Magnetic lines of force drawn to describe the field around a bar magnet would look very much like the pattern of iron filings shown in
Figure 17-4 .
Remember that a magnetic field is not really made up of lines like those in Figure 17-4. Magnetic lines of force are imaginary. In a way, lines of force are like lines drawn on maps. You know that the equator is not really a line around the earth. But a line is often put on a globe to show the location of the equator.
Magnetic lines of force are used for the same reason that lines, such as the equator, are used on globes. They help us "see" something that is not really visible.
* How do you think you could show that there is a magnetic field around a lodestone?
A magnet has these properties:
Two unlike poles-north and south. One pole is at each end.
If a bar magnet is cut in two, two magnets are formed. Each magnet will have a north and south pole.
Like poles of a magnet repel. Unlike poles of a magnet attract.
Lines of force, forming a magnetic field, surround a magnet.
The magnetic field can be revealed by covering the magnet with iron filings.
A magnet attracts iron, cobalt, and nickel.
A magnet can magnetize iron, cobalt, and nickel if a piece of one of these metals is stroked with the magnet.
When a magnet is free-floating, the poles of the magnet line up with the earth's north and south magnetic poles.
A magnet can cause electric currents in conductors. If a bar magnet is moved back and forth inside a coil of wire, an electric current is produced in the wire.
iron filings – залізні ошурки magnetic field – магнітне поле
noticeable – помітний electric current – електричний струм