Electromagnets

Any electric current, or movement of charge carriers, produces a magnetic field. This field can become intense in a tightly coiled wire having many turns and carrying a large electric current. When a ferromagnetic rod, called a core, is placed inside the coil, the magnetic lines of flux are concentrated in the core, and the field strength in and near the core becomes tremendous. This is the principle of an electromagnet (Fig. 1).
Electromagnets are almost always cylindrical in shape. Sometimes the cylinder is long and thin; in other cases it is short and fat. Whatever the

Fig. 1. A simple electromagnet.

ratio of diameter to length for the core, however, the principle is always the same: The flux produced by the current temporarily magnetizes the core.