Electromagnetism Electromagnetism

More Research From his experiments,
Oersted concluded that an
electric current produces a magnetic
field and that the direction
of the magnetic field depends on
the direction of the current. The
French scientist André-Marie
Ampère heard about Oersted’s
findings and did more research
with electricity and magnetism.
Together, their work was the first
research conducted on electromagnetism.
Electromagnetism is
the interaction between electricity
and magnetism.
Using Electromagnetism
Although the magnetic field created by an electric current in
a wire may deflect a compass needle, it is not strong enough
to be very useful. However, two devices, the solenoid and
the electromagnet, strengthen the magnetic field created by a
current-carrying wire. Both devices make electromagnetism
more useful for practical applications.
Solenoids The scientists mentioned at the beginning of this
chapter used a solenoid to levitate a frog. A solenoid is a coil of
wire that produces a magnetic field when carrying an electric
current. A single loop of wire carrying a current does not have
a very strong magnetic field. However, if many loops are used
to form a coil, the magnetic fields of the individual loops can
combine to produce a much stronger magnetic field. In fact, the
magnetic field around a solenoid is very similar to the
magnetic field of a bar magnet, as shown in
Figure 14. The strength of the magnetic field
produced by a solenoid increases as more
loops are added and as the current
in the wire is increased.
Figure 14 The ends of the solenoid
are like the poles of a magnet.
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Compasses Near Magnets
If you try to use a compass near
devices that have strong magnets,
electromagnets, or electric motors,
such as stereo speakers, radios, and televisions, you might
notice that the needle of the compass does not always
point to the north. Use the results from Oersted’s experiments
to explain why this occurs. Why do you think it is
important for a boater to keep the navigation compass
away from the boat’s radio?
Electromagnetism 463