b. Electricity and magnetism are very closely associated, because when
electric current passes through a wire a magnetic field is created around the wire
(fig 13).
Figure 13.
Magnetic field around wire.
c. When a wire carrying electric current is wound into a coil, a magnetic
field with N and S poles is created just as in a bar magnet. Using the "Right-Hand
Rule"--wrapping the fingers around the coil in the direction of current flow--the
thumb will point toward the North or N pole (fig 14).
Figure 14.
Right-hand rule.
d. If an iron core is placed inside the coil, the magnetic field becomes
much stronger because iron conducts magnetic lines much easier than air (fig 15).
This arrangement, called an electromagnet, is used in generators to create strong
magnetic fields by winding many turns of current-carrying wire around iron cores
called pole pieces.
Figure 15.
Iron core coil.
OS 010, 1-P7
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