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UNIT FIVE: Electricity and Magnetism. Chapter 16 Electricity Chapter 17 Magnetism. Chapter Seventeen: Magnetism. 17.1 Properties of Magnets 17.2 Electromagnets 17.3 Electric Motors and Generators 17.4 Generating Electricity. Chapter 17.3 Learning Goals.
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UNIT FIVE: Electricity and Magnetism • Chapter 16 Electricity • Chapter 17 Magnetism
Chapter Seventeen: Magnetism • 17.1 Properties of Magnets • 17.2 Electromagnets • 17.3 Electric Motors and Generators • 17.4 Generating Electricity
Chapter 17.3 Learning Goals • Describe the role of electromagnetism in the function of electric motors and generators. • Contrast energy transformations in electric motors and generators. • Explain the principle of electromagnetic induction.
17.3 Electric motors and generators • Permanent magnets and electromagnets work together to make electric motors and generators. • The secret is in the ability of an electromagnet to reverse its north and south poles.
17.3 Electric motors • Around the edge of a disk are several magnets, their alternating north and south poles facing out.
17.3 Electric motors • To make the disk spin, you bring a permanent magnet close to its edge. • The free magnet attracts one of the magnets in the disk and repels the next one. The disk is a “rotor” because it rotates.
17.3 Electric motors • In a working electric motor, an electromagnet replaces the magnet you reversed with your fingers. • The electromagnet switches its poles to make the rotor keep turning.
17.3 Electric motors • As the rotor spins, a commutatorreverses the direction of the current in the electromagnet.
17.3 Electric motors Motors have three parts: • A rotor with magnets that alternate. • One or more fixed magnets around the rotor. • A commutator that switches the direction of current to keep the rotor spinning.
17.3 Battery run electric motors • An electric motor that runs from batteries has the same three parts. • The permanent magnets are on the outside, and the electromagnets turn in the rotor.
17.3 Battery run electric motors • A simple battery powered motor has three electromagnets in the armature.
17.3 Electromagnetic induction • Motors transform electrical energy into mechanical energy. • Electric generatorsdo the opposite. • They transform mechanical energy into electrical energy. • The process of using a moving magnet to create electric current is called electromagnetic induction.
17.3 Electromagnetic induction • A moving magnet produces a current in a coil of wire.
17.3 Generating electricity • A generatorconverts mechanical energy into electrical energy using the law of induction. • As long as the disk is spinning, there is a changing magnetic field through the coil and electric current is created.
Key Question: How does an electric motor work? Investigation 17C Electromagnetic Forces