# Generators and Motors 15 HSW LU Hours

## Quiz Questions

 1. Generators convert mechanical motion to electrical energy using what principle? Magnetic induction. Magnetic electricity. 2. What rule should you use to determine the direction of induced emf in a coil? The left-hand rule for generators. The right- hand rule 3. What is the purpose of the slip rings? To conduct the currents induced in the armature to an external load To avoid static electricity 4. Why is no emf induced in a rotating coil when it passes through the neutral plane? No flux lines are cut. The coil is rotating 5. What component causes a generator to produce dc voltage rather than ac voltage at its output terminals? A commutator A rotating coil 6. At what point should brush contact change from one commutator segment to the next? The point at which the voltage is zero across the two segments The point at which the voltage is highest across the two segments 7. An elementary, single coil, dc generator will have an output voltage with how many pulsations per revolution? Two Three 8. How many commutator segments are required in a two-coil generator? Four Six 9. How can field strength be varied in a practical dc generator? By varying the input voltage to the field coils. By varying the output voltage to the field coils. 10. What causes sparking between the brushes and the commutator? Improper commutation. Too much electricity 11. The reaction of the armature is distortion of the main field due to the effects of armature current. True False 12. The purpose of interpoles is to counter act armature reaction True False 13. What is the effect of motor reaction in a dc generator? A force which causes opposition to applied turning force. A force in the same direction to turning force 14. What causes copper losses? Resistance in the armature coils, which increases with temperature. Friction 15. How can eddy current be reduced? By laminating the core material. By reducing the current. 16. Why are drum-type armatures preferred over the Gramme-ring armature in modern dc generators? Drum-type armatures are more efficient, because flux lines are cut by both sides of each coil Drum-type armatures are bigger. 17. Lap windings are used in generators designed for what type of application? Higher load currents are possible. Lower load currents are possible. 18. What are the three classifications of dc generators? Series-wound, shunt-wound, and compound-wound Dc generators have four classifications 19. What is the main disadvantage of series generators? Output voltage varies as the load varies Output voltage stays steady regardless of load input 20. What term applies to the voltage variation from no-load to full-load conditions and is expressed as a percentage? Voltage regulation. Voltage Amp.