Chapter 36

Magnetism

The Big Idea

A changing electric field makes a

magnetic field.

This means that a moving charge

makes a magnetic field.

James Maxwell

Some Facts• We use the letter B to represent the

magnetic field.

• It is a vector field.

• It is measured in Teslas or

Webers or Gauss.

Tesla

Weber

Gauss

Magnetic Poles

• Two Poles: North and South.

• Magnetic poles always exist in pairs.

• Keep breaking a magnet in half and you will never isolate a single pole.

Magnetic Fields• Compare the magnetic field produced

by a bar magnet and the electric field produced by two charges.

Magnetic Field from a bar magnet

Electric Field from two opposite charges

Magnetic Field Produced by a Current in a wire.

• Use the “Right Hand Rule”

• With your right hand point your thumb towards the direction that the current flows.

• As you curl your fingers, the magnetic field points the way your fingers do.

One more important Fact

• A changing magnetic field will create an electric field.

• When this electric field is created by a conductor, a current will flow through the conductor.

• The current in the conductor is said to be induced.

Induction

• Using a changing magnetic field to induce a current is how all electricity is made.

• Nikola Tesla is THE man who created the AC generator. His device uses magnets to induce an alternating current in a wire.

Other source of magnetic Fields

• Some material, by it’s nature, is magnetic.