AC Theory 3: Lesson 5 - Introduction To Generators

Question 1

Generators are electromechanical devices that turn _____ energy into ______ energy.

a. electrical / mechanical
b. kinetic / potential
c. mechanical / electrical
d. potential / heat

Answer 1

c. mechanical / electrical

Question 2

The source for mechanical motion supplied to a generator is referred to as the ______.

a. driver
b. engine
c. originator
d. prime mover

Answer 2

d. prime mover

Question 3

In order to induce electrical energy into a conductor or generator, what three factors must be present?

I. Conductor
II. Heat
III. Magnetic field
IV. Relative motion
V. Rotation

a. I., II., and III.
b. I., III., and IV.
c. I., III., and V.
d. II., III., and V.

Answer 3

b. I., III., and IV.

Note: In a transformer, voltage is induced into the secondary coil without any mechanical rotation; relative motion between a magnetic field and a conductor will induce voltage in that conductor.

Question 4

Match the correct part of the alternator with the corresponding letter.

Armature windings or loops
Brush
Magnetic field poles
Slip ring

Answer 4

B - Armature windings or loops
D - Brush
A - Magnetic field poles
C - Slip ring

Question 5

When using the Fleming left hand rule for generators, the thumb indicates the direction of thrust, the forefinger indicates the direction of field flux from N to S, and the center finger indicates the direction of induced current.

True or False

Answer 5

True

Question 6

If there is an external circuit for current to flow, electron current will flow from the ______ to the ______ terminal in the circuit.

a. load / source
b. negative / positive
c. positive / negative
d. source / load

Answer 6

b. negative / positive

Note: Be aware that this is the external circuit, and that internally to the generator it looks like current is flowing to the negative terminal.

Question 7

The rotating armature of an AC generator is connected to its external circuit through ______ while a DC generator uses a(n) ? to make the connection.

a. brushes / rotor
b. commutators / slip ring
c. rotors / brush
d. slip rings / commutator

Answer 7

d. slip rings / commutator

Question 8

The winding in a generator where voltage is induced is called the ______.

a. armature
b. commutator
c. exciter
d. slip ring

Answer 8

a. armature

Question 9

A single coil generator spinning in a magnetic field will produce a full sine wave for every ______ of rotation.

a. 90°
b. 180°
c. 360°
d. 720°

Answer 9

c. 360°

Question 10

The measure of how frequently a generator produces a sine wave is called the ______ of the waveform.

a. cycles
b. frequency
c. hertz
d. period

Answer 10

b. frequency

Question 11

AC generators can be constructed in two basic styles and can be described as a ______ type or a ______ type generator.

a. brush / brushless
b. commutating / non commutating
c. revolving armature / revolving field
d. slip ring / commutator

Answer 11

c. revolving armature / revolving field

Question 12

Increasing the turns or loops of wire on the rotating armature of a generator would cause a(n) ______ output of the generator.

a. decrease of current
b. decrease of voltage
c. increase of current
d. increase of voltage

Answer 12

d. increase of voltage

Question 13

A revolving armature AC generator has each end of the rotating loops or winding connected to what component(s)?

a. the armature
b. the brushes
c. the commutator
d. the slip rings

Answer 13

d. the slip rings

Question 14

Increasing the speed of rotation or increasing the flux field strength are both ways to increase the output voltage of a generator without making physical changes to the machine.

True or False

Answer 14

True

Question 15

A 4-pole generator will be supplying several loads that are designed for 60 hertz. At what speed does the generator need to be driven?

______ RPM

Answer 15

1800 RPM

Question 16

The revolving field AC generator has the armature windings positioned around the generator housing. The name given to the armature in this case is called the ______.

a. coil
b. exciter
c. flux field
d. stator

Answer 16

b. exciter

Question 17

The abbreviation PMG stands for a type of generator that uses ______ for the flux field.

a. perfect magnets
b. permanent magnets
c. potential magnets
d. pulse magnets

Answer 17

b. permanent magnets

Question 18

A rotating field AC generator is connected to the DC voltage source through slip rings.

True or False

Answer 18

True

Question 19

The DC voltage and current that is supplied to the field of a generator is called the ______ power.

a. armature
b. exciter
c. flux
d. input

Answer 19

b. exciter

Question 20

One full revolution of a 4-pole generator will result in ______ cycle(s) of output.

a. one-half
b. one
c. two
d. four

Answer 20

c. two