ELECTRICITY AND MAGNETISM 22.3

# ELECTRICITY AND MAGNETISM 22.3

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## ELECTRICITY AND MAGNETISM 22.3

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1. ELECTRICITY AND MAGNETISM 22.3

2. Chapter Twenty-Two: Electricity and Magnetism • 22.1 Properties of Magnets • 22.2 Electromagnets • 22.3 Electric Motors

3. Chapter 22.3 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.

4. 22.3 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.

5. 22.3 Electric motors • Around the edge of a disk are several magnets, their alternating north and south poles facing out.

6. 22.3 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.

7. 22.3 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.

8. 22.3 Electric motors • As the rotor spins, a commutator reverses the direction of the current in the electromagnet.

9. 22.3 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.

10. 22.3 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.

11. 22.3 Battery run electric motors • A simple battery powered motor has three electromagnets.

12. 22.3 Electromagnetic induction • Motors transform electrical energy into mechanical energy. • Electric generators do the opposite. • They transform mechanical energy into electrical energy. • The process of using a moving magnet to create electric current is called electromagnetic induction.

13. 22.3 Electromagnetic induction • A moving magnet produces a current in a coil of wire.

14. 22.3 Generating electricity • A generator converts 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.

15. Key Question: How does an electric motor work? Investigation 22C Electromagnetic Forces

16. Under the Sea • Have you ever wondered what it would be like to take a “walk” on the seafloor? Engineer Jim Varnum gets to go “down under” regularly, because he is a pilot of an extremely complex robot called Jason II. This robot dives deep into the ocean and is used to take pictures and collect data from the seafloor.