Chapter 9 Review Questions

Fred Bear MAIR 1449.02 3-24-11 R.Q. Unit 9 (E.B.) 1. What is magnetism? When two pieces of iron are attracted to each other by physical means or electrical means. 2. Torque is A. Strength that a motor produces by turning. 3. A magnetic field is D. All the above. 4. True or False: A permanent magnet is a piece of material that has been magnetized and can hold its magnetic strength for a reasonable length of time. True. 5. How is an electromagnet produced? Through electricity. 6. Which of the following produces the best electromagnet? B. soft iron 7. Unlike poles of a magnet repel each other and like poles attract each other. 8. What part does polarity play in the operation of an electric motor? It allows the motor to run continuously. 9. What part of a motor produces an inductive magnetic field within itself to facilitate the rotating motion? Rotor and stator. 10. What part does the frequency of alternating current play in the operation of an electric motor? Helps change polarity 120 times a second. 11. What would be the speed of a two-pole motor operating on a 120 volts 60 Hertz power supply? 3450rpm 12. What are the five types of single-phase motors used in the industry? 13. Which of the following correctly lists the motor’s starting torque from lowest to highest? B. Shaded pole, three phase, permanent split capacitor, capacitor start.

14. Which of the following is a common use of a shaded pole motor? A. Furnace fan motor.

15. How does a shaded pole motor operate? The shaded poles produce a magnetic field that is out of phase with the magnetic field of the main winding.

16. How can a shaded pole motor be reversed? The stator must be reversed to change the positions of the shaded poles, and this usually means disassembling the motor.

17. What determines the rotation of a shaded pole motor? B. Location of shaded pole.