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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.