Deck 31: Direct Current Motors

Question 1

Counter-electromotive force (CEMF) and back-EMF are names for the voltage induced into the armature of a DC motor.

Answer 1

True

Question 2

The pushing or turning force created by the magnetic field of the pole pieces and the magnetic field of the loop or armature is called _______________.

Answer 2

torque

Question 3

The motor that does not contain a wound armature, commutator, or brushes is the _____ motor.

A) servo
B) stepping
C) selsyn
D) brushless DC

Answer 3

D

Question 4

When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor.

A) series
B) shunt

Question 5

The compound motor connection that should generally be avoided is the _____.

A) cumulative
B) differential

Question 6

A device that converts electrical energy into mechanical energy is called a(n) _____.

A) alternator
B) generator
C) motor
D) inverter

Question 7

In a compound DC motor control circuit, the field loss relay will disconnect the _____ if power is lost to the _____.

A) rotor; armature
B) armature; shunt field
C) shunt field; armature
D) armature; rotor

Question 8

The servomotor featuring a fiberglass and copper rotor is the _____ motor.

A) copper
B) copper-glass
C) nonferrous
D) ServoDisc

Question 9

Small permanent magnet motors that have lightweight rotors are often used as _____.

A) stepping motors
B) automobile starters
C) servomotors
D) ceiling fans

Question 10

Permanent magnet motors have _____ efficiency than conventional field-wound motors.

A) higher
B) lower

Question 11

A series motor may be operated with no load connected.

Question 12

A square wave voltage varies between 0 V and 12 V. The positive pulses are 75 μ s wide and there is a 25 μ s gap between them. What is the DC average of the waveform?

A) 3 V
B) 4 V
C) 6 V
D) 9 V

Question 13

The speed of the disc servomotor can be varied by changing the amount of voltage supplied to the armature. The voltage is generally varied using _____.

A) phase
B) pulse-width
C) frequency
D) amplitude

Question 14

The ServoDisc motor is also often called a _____ motor.

A) copper
B) laminated
C) printed-circuit
D) nonferrous

Question 15

When a motor is connected differential compound, the _____ determines the direction of rotation of the motor at no load or light load.

A) shunt field
B) armature
C) rotor
D) load

Question 16

A square wave voltage varies between 0 V and 12 V. The positive pulses are 50 μ s wide and there is a 50 μ s gap between them. What is the DC average of the waveform?

A) 3 V
B) 4 V
C) 6 V
D) 9 V

Question 17

A compound motor has _____ field windings.

A) series
B) shunt
C) series and shunt
D) combined

Question 18

The DC motor, known as a "constant speed motor," is the _____ motor.

A) series
B) shunt

Question 19

A square wave voltage varies between 0 V and 12 V. The positive pulses are 25 μ s wide and there is a 75 μ s gap between them. What is the DC average of the waveform?

A) 3 V
B) 4 V
C) 6 V
D) 9 V

Question 20

The speed regulation of a DC motor is proportional to the _____.

A) applied voltage
B) load torque
C) armature resistance
D) field resistance

Question 21

When a DC machine is used as a generator, the _______________ performs the function of a mechanical rectifier to change the AC produced in the armature into DC before it exits the machine through the brushes.