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Discovery of Electromagnetism

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Discovery of Electromagnetism

Tamara made the simple device in this picture for science class. She wrapped a wire around a nail and connected the ends of the wire to the terminals of a battery. The nail is attracting paper clips, so it appears to have become magnetized. The device isn’t complicated, but it shows a very important relationship.

Q: What does Tamara’s device show?

A: The device shows that you can use electricity to create magnetism.

Electricity and Magnetism

Magnetism produced by electricity is called electromagnetism . Today, electromagnetism is used in many electric devices. However, until electromagnetism was discovered, scientists thought that electricity and magnetism were unrelated. A Danish scientist named Hans Christian Oersted (pictured in the Figure below ) changed all that. He made the important discovery that electric current creates a magnetic field. But like many other important discoveries in science, Oersted’s discovery was just a lucky accident.

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 are not related. 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. The well-known picture below depicts Oersted’s landmark discovery.

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 the Figure below . 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

From 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 induction. It occurs when a conductor, such as a wire, crosses lines of force in a magnetic field. This can happen when a wire is moving relative to a magnet or a magnet is moving relative to a wire.

Summary

  • Electricity can be used to produce a magnetic field. Magnetism produced by electricity is called electromagnetism.
  • In 1820, Oersted discovered by accident that electric current creates a magnetic field. Prior to that, scientists thought that electricity and magnetism were unrelated.
  • Oersted also used a compass to find the direction of the magnetic field around a wire carrying current.
  • Around 1830, Michael Faraday discovered that a magnetic field can generate an electric current if a conductor crosses the lines of force in a magnetic field. This is known as Faraday’s law.

Vocabulary

  • electromagnetism : Magnetism produced by electric current.
  • Faraday’s law : Law stating that a changing magnetic field produces an electric current in a conductor.

Practice

At the following URL, review Oersted’s discovery of electromagnetism. Also read how the famous magician Houdini used electromagnetism in one of his most famous magic tricks. Then take the quiz at the bottom of the Web page. http://weeklysciencequiz.blogspot.com/2011/10/discovery-of-electromagnetism.html

Review

  1. What observation led Oersted to conclude that electricity and magnetism are related?
  2. How did Oersted find the direction of the magnetic field around a wire carrying current?
  3. What did Faraday discover?

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