Deck 31: Direct Current Motors

Question 1

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 1

D

Question 2

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

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

Answer 2

C

Question 3

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

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

Answer 3

C

Question 4

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 5

A series motor may be operated with no load connected.

Question 6

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

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

Question 7

A compound motor has field windings.

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

Question 8

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

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

Question 9

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

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

Question 10

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

A) cumulative
B) differential

Question 11

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 12

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 _.

Question 13

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

A) higher
B) lower

Question 14

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 15

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

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

Question 16

A square wave voltage varies between 0 V and 12 V. The positive pulses are 25 μs wide and there is a 75 μs 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

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

Question 18

The ServoDisc motor is also often called a motor.

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

Question 19

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 20

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

A) series
B) shunt

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.