Magnets and Electromagnets

Magnets and Electromagnets

1. Definition

   • Magnets create a magnetic force between one another and between themselves and magnetic materials.

2. Magnetism

   • Magnets can attract and repel one another. They also attract magnetic materials.
   • Magnetic materials are attracted to magnets but not to each other. Examples of magnetic materials are; iron, steel and nickel.
   • Non-magnetic materials are not affected at all by magnets.
   • The magnetic force passes through non-magnetic materials but not through magnetic materials.
   • The ends of magnets are called poles. The south-seeking pole points south and the north seeking pole points north.
   • A north-seeking pole and a south-seeking pole attract each other, but two south-seeking poles or two north-seeking poles repel each other.

3. Magnetic Field

   • The area around magnets is called the magnetic field. Magnetic field lines can be plotted with a compass.
   • The direction of the magnetic field goes from the magnet's north pole to its south pole.
   • Stronger magnets are represented by showing more lines of force around them.
   • The Earth behaves as if it had a giant magnet inside it.
   • The magnet in a compass lines up with the Earth's magnetic field.

4. Own magnet

   • You can make your own magnet by stroking an iron nail with one end of a magnet.

5. Electromagnet

   • When an electric current flows through a wire, the wire behaves like a weak magnet.
   • Magnets made using electricity are called electromagnets. These contain a core, usually of iron, and a coil of wire which carries an electric current.
   • Electromagnets are very useful because they can be switched on and off.
   • You can change the strength of an electromagnet by changing the size of the current, coiling the wire or placing a piece of iron inside the coil of wire.

6. Relays

   • Relay switches use the current from one circuit to switch on the current in another circuit.
   • A relay switch has an electromagnet in one circuit next to an iron switch in the other circuit.