Table Of Contents: Magnetism
1. What Is a Magnet?
A magnet is a substance that attracts the element iron or materials that contain iron. All magnets have opposite ends called the north pole and the south pole. Similar magnetic poles repel each other, and opposite poles attract each other.
2. Magnetic Forces, Poles and Fields
The degree to which magnets repel or attract each other depends on their magnetic forces. The greatest magnetic force is located at the poles of a magnet, but there is an area all the way around the magnet that displays magnetism. This area is called its magnetic field. In this diagram, the lines represent the magnetic force around the magnet. The closer the lines are, the greater the magnetic force. The arrows show the direction of the field.
3. Inside a Magnet
Inside a magnet there are clusters of atoms known as magnetic domains that are responsible for magnetic properties. If the atoms with similar magnetic fields within a domain line up in the same direction, they are said to be magnetized. Atoms that are arranged in random directions within a domain are considered to be non-magnetic. Natural elements that can be magnetic include iron, nickel, cobalt, gadolinium, samarium and neodymium.
4. Earths Magnetic Field
Deep in the Earth, the convection currents in the liquid iron core create a magnetic field that impacts the Earths magnetism. The Earth acts like a giant magnet, having two opposite poles and a strong magnetic field. The Earth's geographic poles are at a slightly different location than the Earths magnetic north and south poles. The positions of the magnetic poles are dynamic and they shift from year to year. This map shows the changing position of the north magnetic pole in recent history.
When an electric current flows through a coil of wire, a magnetic field is produced. This relationship between electricity and magnetism is called electromagnetism. The magnetism of an electromagnet can be controlled by switching the electric current on or off. Electromagnets are used in many devices including computers, doorbells, and cranes that pick up heavy loads.