Figure 2-8. Magnetic permeability.
(Nonmagnetic materials have no effect on magnetic lines of force (A), but magnetic
materials intensify the lines by drawing them from the air and concentrating them within
a. Magnetic and electrical phenomena are closely related--electricity always
produces magnetism. Magnetism caused by an electric current flowing through a
conductor is called electromagnetism. In 1820, the Danish scientist Oersted observed
that a compass or suspended bar magnet was deflected when placed near a wire
carrying an electric current and returned to its original position when the current ceased.
b. A wire carrying a current of electricity has around it a field of force that acts on
iron filings placed on a cardboard in a manner similar to the field of force around a
permanent magnet (figure 2-9).
Figure 2-9. Electromagnetic lines of force around a current-carrying wire.