Magnetism from electricity

A connection between electricity and magnetism was discovered (accidentally) by Orsted over 100 years ago, who noticed that a compass needle is deflected when brought into the vicinity of a current carrying wire. Thus, currents induce in their vicinity magnetic fields. An electromagnet is simply a coil of wires which, when a current is passed through, generate a magnetic field, as below.

  

Figure 9.10: Electromagnet

Another example of this effect at work is in an atom, such as pictured in Fig. 9.1 - since an electron is a charge which moves about the nucleus, in effect it forms a current loop, and hence a magnetic field may be associated with an individual atom. It is this basic property which is believed to be the origin of the magnetic properties of various types of materials found in nature, as we shall now discuss.