# discovery of electromagnetism

## 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 didnt move. It just kept pointing toward Earths north magnetic pole. After the demonstration, a curious student held the wire near the compass again, but in a different direction. To Oersteds 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.

## 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 1.1) changed all that. He made the important discovery that electric current creates a magnetic field. But like many other important discoveries in science, Oersteds discovery was just a lucky accident.

## 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 1.2. The lines of magnetic force circle around the wire in a counterclockwise direction.

## 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 Faradays 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.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

the discovery described in question 2 was made by accident.

``````-->  a. true

b. false
``````

electromagnetism was discovered when a scientist was trying to show that electricity and magnetism

``````a) are the same thing.

b) are closely related.

-->  c) are unrelated.

d) none of the above
``````

electric current creates a magnetic field.

``````-->  a. true

b. false
``````

a magnetic field creates an electric current.

``````-->  a. true

b. false
``````

``````a) electricity

b) magnetism

c) electromagnetism

-->  d) electromagnetic induction
``````

electromagnetism is no longer commonly used.

``````a. true

-->  b. false
``````

## diagram questions

No diagram questions associated with this lesson