1. U3e-L8 1.What does the following schematic symbol represent? 2.What does the following schematic symbol represent? 3.How many volts are typical in a residential electrical outlet? 4.What do graphs of DC and AC power sources look like? Why? March 04, 2010 DRILL DC Power Supply AC Power Supply 120 volts

2. If voltage is constantly 1.5 V, what does its graph over time look like? Direct Current Time (seconds) Voltage (volts) 0 2 4 6 8 10 12 14 1 2 3 1.5 V U3e-L8

3. If voltage is alternating 120 V to -120 V, what does its graph over time look like? Alternating Current Time (seconds) Voltage (volts) 0 2 4 6 8 10 12 14 -120 0 120 +/-120 V U3e-L8

4. Michael Faraday (1791-1867) –London, England. –Physicist and Chemist First person to successfully create an electric motor. Discovered that electric currents create a magnetic field, and vice versa. Electric Motors

5. To demonstrate the principle of electromagnetism. To use principles of electromagnetism to produce a mechanical result. Purpose of Lesson U3e-L8

6. 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 NSNS ATTRACT REPEL NS

7. 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 U3e-L8

8. NSNS ELECTRIC 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.

9. NS NS 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 U3e-L8

10. What is a schematic? How would a schematic which includes an electric motor look? ELECTRIC MOTORS A schematic is a diagram that represents the elements of a system without using realistic pictures. V = 9V I Motor Switch = Commutator U3e-L8

11. 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 U3e-L8

12. ELECTRIC MOTORS 120 V Lamp U3e-L8

13. HOMEWORK Finish reading the article about magnetism and motors (Maglev Trains) and answering the questions. Due tomorrow. U3e-L8