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Transcript
April 9, 2008 DRILL 1. Have out your electric motor project. 2. Who was the first person to successfully create an electric motor? Michael Faraday 3. What was this man’s profession? Physicist and Chemist 4. What did he discover? Electric currents create a magnetic field and magnetic fields induce electric currents. U3e-L16 ELECTRIC MOTORS • • 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 _____________ ATTRACT • Like poles _____________ REPEL N S S S N N U3e-L16 ELECTRIC MOTORS • • 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. U3e-L16 ELECTRIC MOTORS – What will happen now? – The electromagnet and the permanent magnet will ATTRACT each other. N S • The electromagnet and the permanent magnet will REPEL each other. S N • • Back to our magnet: Suppose we create an electromagnet like below. What will happen? U3e-L16 ELECTRIC MOTORS • • • 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. N S U3e-L16 ELECTRIC MOTORS 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? U3e-L16 ELECTRIC MOTORS 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? U3e-L16 ELECTRIC MOTORS What is a schematic? A schematic is a diagram that represents the elements of a system without using realistic pictures. How would a schematic of your electric motor look? Switch = Commutator Load V = 9V U3e-L16 I ELECTRIC MOTORS • 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. U3e-L16 ELECTRIC MOTORS Lamp 120 V U3e-L16 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. U3e-L16