1. Have out your electric motor project.

2. Who was the first person to successfully create an electric motor?

3. What was this man’s profession?

4. What did he discover?

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April 9, 2008

DRILL

Michael Faraday Physicist

and Chemist

Electric currents create a magnetic field and magnetic fields induce electric currents.

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• Electric motors are used everyday in many ways.• A motor’s purpose is to turn electrical energy into

mechanical energy.

Motors work on simple principles of magnetism:• Opposite poles _____________• Like poles _____________

ELECTRIC MOTORS

N SN S

ATTRACT

REPEL

NS

• An electric current produces a magnetic field.• Electric current through a coil of wire creates an

electromagnet.• What is the benefit of creating a magnet with

electricity?– It can be turned on and off.– The strength and direction of the magnetic

poles can be controlled by altering the strength and direction of the electric current.

ELECTRIC MOTORS

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N S

NSELECTRIC MOTORS

Back to our magnet:• Suppose we create an electromagnet like below.• What will happen?

– The electromagnet and the permanent magnet will REPEL each other.

• What will happen now?– The electromagnet and the permanent magnet will

ATTRACT each other.

N

S

N S

• What would happen if we put an axle through the middle of the permanent magnet, then turned on the electromagnet?

• This is how a motor rotates.• The electromagnet is turned on and off so that the

permanent magnet is attracted, then repelled, then attracted, then repelled….and so on.

ELECTRIC MOTORS

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Let’s look at your electric motor project• Identify the following:

– Permanent Magnets– Electromagnet

• How is the electromagnet powered?• What is the circuit that the current must follow?• If your motor were working ideally, how is the

electromagnet turned on and off to cause CONSTANT rotation?

ELECTRIC MOTORS

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The commutator turns the electromagnet on and off at particular times.

When does it turn the magnet on?

When does it turn the magnet off?

ELECTRIC MOTORS

What is a schematic?

How would a schematic of your electric motor look?

ELECTRIC MOTORS

A schematic is a diagram that represents the elements of a system without using realistic pictures.

V = 9V

I

Load

Switch = Commutator

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• Now that you know what switches look like in electrical schematics, draw an electrical schematic for a lamp plugged into a wall outlet.

• Remember that AC power supplies look like in electrical schematics.

ELECTRIC MOTORS

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ELECTRIC MOTORS

120 VLamp

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HOMEWORK

• Tomorrow is a review for Monday’s test on Electrical Technology.

• Begin studying tonight!• Any problem/question that you’ve seen in class

is a candidate for the test.• Come to class with any questions you may have.

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