5.85. Discovery of Electromagnetism http://www.ck12.org
FIGURE 5.183
An Accidental Discovery
In 1820, Oersted was presenting a demonstration to some science students. Ironically, he was trying to show them
that electricity and magnetism arenotrelated. He placed a wire with electric current flowing through it next to a
compass, which has a magnetic needle. As he expected, the needle of the compass didn’t move. It just kept pointing
toward Earth’s north magnetic pole.
After the demonstration, a curious student held the wire near the compass again, but in a different direction. To
Oersted’s surprise, the needle of the compass swung toward the wire so it was no longer pointing north. Oersted
was intrigued. He turned off the current in the wire to see what would happen to the compass needle. The needle
swung back to its original position, pointing north once again. Oersted had discovered that an electric current creates
a magnetic field. The magnetic field created by the current was strong enough to attract the needle of the nearby
compass.
Oersted Learns More
Oersted wanted to learn more about the magnetic field created by a current. He placed a compass at different
locations around a wire with current flowing through it. You can see what he found in theFigure5.184. The
lines of magnetic force circle around the wire in a counterclockwise direction. You can learn more about Oersted’s
investigations at the URL below.
http://www.youtube.com/watch?v=BM4m2GId3F8
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/5062From Magnets to Electricity
Just about a decade after Oersted discovered that electric current can produce a magnetic field, an English scientist
named Michael Faraday discovered that the opposite is also true. A magnetic field can produce an electric current.
This is known as Faraday’s law. The process by which a magnetic field produces current is called electromagnetic