PLUG 1W2803 - Caterpillar

Introduction to Magnetism
Magnetism is another form of force that causes electron flow or current. A basic understanding of magnetism is necessary to study electricity. Magnetism provides a link between mechanical energy and electricity. The use of magnetism causes an alternator to convert some of the mechanical power developed by an engine to electromotive force (EMF). Magnetism will allow a starter motor to convert electrical energy from a battery into mechanical energy for cranking the engine.The Nature of Magnetism
Most electrical equipment depends directly or indirectly upon magnetism. There are a few electrical devices that do not use magnetism.There are three basic types of magnets:
Natural
Man-made
ElectromagnetsNatural Magnets
The Chinese discovered magnets about 2637 B.C. The magnets that were used in the primitive compasses were called lodestones. Lodestones were crude pieces of iron ore. The lodestones are known as magnetite. Since magnetite has magnetic properties in the natural state, lodestones are classified as natural magnets.Man-made Magnets
Illustration 1 g01069088
Man-made magnets are typically produced in the form of metal bars. These bars have been subjected to very strong magnetic fields. All man-made magnets are produced. These man-made magnets are sometimes referred to as artificial magnets.Electromagnets
A Danish scientist named Oersted discovered a relation between magnetism and electric current. Oersted discovered that an electric current flowing through a conductor produced a magnetic field around the conductor.Magnetic Fields
Every magnet has two points opposite each other which attract pieces of iron. These points are called the poles of the magnet: the north pole and the south pole. Just like electric charges repel each other and opposite charges attract each other, like magnetic poles repel each other and unlike poles attract each other.A magnet clearly attracts a bit of iron because of some force that exists around the magnet. This force is called a magnetic field. Although it is invisible to the naked eye, the force can be shown by sprinkling small iron filings on a sheet of glass or paper over a bar magnet. In Illustration 1, a piece of glass is placed over a magnet and iron filings are sprinkled on the glass. When the glass cover is gently tapped the filings will move into a definite pattern, which shows the field force around the magnet.
Illustration 2 g01069089
The field seems to be made up of lines of force that appear to leave the magnet at the north pole. The lines of force travel through the air around the magnet. The lines of force continue through the magnet to the south pole to form a closed loop of force. The stronger the magnet is, the greater the lines of force are, and the larger the area covered by the magnetic field.Lines of Force
Illustration 3 g01069091
To better visualize the magnetic field without iron filings, the field is shown as lines of force in Illustration 3. The direction of the lines outside the magnet shows the path a north pole would follow in the field, repelled away from the north pole of the magnet and attracted to the south pole. Inside the magnet, which