Post on 01-Oct-2020
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Key Questions�� Why are there magnets in anelectric motor?�� How is the electricity thatpowers all of the appliances inyour home generated?�� What is the purpose of atransformer on a power line?
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Magnetism is created by moving charges, either in an electric current or in the atoms that make up a material.
Electromagnets are magnets created by electric current flowing in wires.
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
The biggest magnet on Earth is the planet itself. Earth has a magnetic field that has been useful to travelers for thousands of years.
As early as 500 B.C. people discovered that some naturally occurring materials had magnetic properties. The Greeks observed that one end of a suspended piece of lodestone pointed north and the other end pointed south,helping sailors and travelers find their way.
A compass is a device containing a magnet that interacts with Earth’s magnetic field to indicate direction.
By 1200, explorers from Italy were using a compass to guide ocean voyages beyond the sight of land
Magnatism Part 2.notebook
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May 01, 2016
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
For a long time, people believed electricity and magnetism were unrelated. As scientists began tounderstand electricity better, they searched for relationships between electricity and magnetism.
1819, Hans Christian Øersted, a Danish physicist and chemist, placed a compass needle near a wire in a circuit. When a switch in a circuit is closed, the compass needle moves just as if the wire were a magnet.
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Magnetism is created by moving charges. Electric current is made of movingcharges
The experiment with the compasses shows that a wire carrying electric currentmakes a magnetic field around it.
The strength of the magnetic field near the wire depends on two factors:
1. The strength is directly proportional to the current, so doubling the currentdoubles the strength of the field.
2. The field strength is inversely proportional to the distance from the wire.The field gets stronger as you move closer to the wire. It gets weaker the farther you get.
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Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Permanent magnets and electromagnets work together to make electric motors and generators.
Electric motors convert electrical energy into mechanical energy.
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Using a single magnet to spina disk of magnets. Reversing the magnet inyour fingers attracts and repels the magnetsin the rotor, making it spin.
The disk is called the rotor because it can rotate.
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and InductionHow the electromagnets in a motor operate
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
All types of electric motors must have three parts They are:1 A rotating part (rotor) with magnets that alternate.
2 One or more fixed magnets around the rotor.
3 A commutator that switches the direction of current in the electromagnetsback and forth in the right sequence to keep the rotor spinning.
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
Magnatism Part 2.notebook
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May 01, 2016
Chapter17 Electromagnets and Induction
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May 01, 2016
Chapter17 Electromagnets and Induction
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May 01, 2016
Chapter17 Electromagnets and Induction