Earth and Electromagnetic Induction:

April 2014

Earth as a Magnet:

• All matter is made of atoms. Electrons are negatively charged particles of atoms. As an electron moves around, it makes, or induces, a magnetic field.

• The atom will then have a north and a south pole. In most materials, such as copper and aluminum, the magnetic fields of the individual atoms cancel each other out. Therefore, these materials are not magnetic.– What does this mean?

Earth as a Magnet:

• What does a compass point to?– What does geographic mean? Magnetic?– Which one does a compass point to?

• A compass needle points north because the magnetic pole of Earth that is closest to the geographic North Pole is a magnetic south pole.

Picture is worth a 1000 ?’s

Quick Check:

• What are the 3 parts of an electromagnet?

• How can you make it stronger?

Electromagnetic Induction:

• We saw how to use electricity to make a magnet…but what about a magnet to make electricity?

• Electromagnetic induction: p. 439– How does it work?– How can you strengthen it?

• Process that causes an electric current in a changing a magnetic field

Electromagnetic Induction:

• Electromagnetic induction: p. 439– What is needed? Parts?

• Magnet• Coils of copper wire

Picture of this:

Galvanometer

• Galvanometer- a device that uses an electromagnet to measure electric current– Examples: gas indicator, engine light, oil temperature– Current changes as temperature changes, needle is

connected to an electromagnet, which is suspended so it can rotate between the poles of a permanent fixed magnet

– When current flows through the coil, the electromagnet rotates

• http://www.hometrainingtools.com/articles/homemade-galvanometer.html

Electric motors• When more current flows through the coil, the

electromagnet’s magnetic field becomes stronger– The magnetic force between the coil and the

permanent magnet increases, and the coil turns faster

– Extra info: http://www.physclips.unsw.edu.au/jw/electricmotors.html

Review:

• Oersted discovered that a wire carrying a current makes a magnetic field.

• Electromagnetism is the interaction between electricity and magnetism.

• An electromagnet is a solenoid that has an iron core.

• A magnet can exert a force on a wire carrying a current.

• A doorbell, an electric motor, and a galvanometer all make use of electromagnetism.