DC Motors Mcqs - Set 2

1)   In a D.C. shunt motor, speed is______________?

a. independent of armature current
b. directly proportional to the armature current
c. proportional to the square of the current
d. inversely proportional to the armature current
Answer  Explanation 

ANSWER: independent of armature current

Explanation:
No explanation is available for this question!


2)   A direct on line starter is used: for starting motors___________?

a. up to 5 H.P
b. up to 10 H.P
c. up to 15 H.P
d. up to 20 H.P
Answer  Explanation 

ANSWER: up to 5 H.P

Explanation:
No explanation is available for this question!


3)   What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?

a. The motor will stop
b. The motor will continue to run
c. The armature may burn
d. The motor will run noisy
Answer  Explanation 

ANSWER: The armature may burn

Explanation:
No explanation is available for this question!


4)   In case of D.C. shunt motors the speed is dependent on back e.m.f. only because____________?

a. back e.m.f. is equal to armature drop
b. armature drop is negligible
c. flux is proportional to armature current
d. flux is practically constant in D:C. shunt motors
Answer  Explanation 

ANSWER: flux is practically constant in D:C. shunt motors

Explanation:
No explanation is available for this question!


5)   In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be_____________?

a. almost negligible
b. rated full-load current
c. less than full-load current
d. more than full-load current
Answer  Explanation 

ANSWER: more than full-load current

Explanation:
No explanation is available for this question!


6)   These days D.C. motors are widely used in____________?

a. pumping sets
b. air compressors
c. electric traction
d. machine shops
Answer  Explanation 

ANSWER: electric traction

Explanation:
No explanation is available for this question!


7)   By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

a. Frame
b. Shaft
c. Commutator
d. Stator
Answer  Explanation 

ANSWER: Commutator

Explanation:
No explanation is available for this question!


8)   In which of the following applications D.C. series motor is invariably tried?

a. Starter for a car
b. Drive for a water pump
c. Fan motor
d. Motor operation in A.C. or D.C
Answer  Explanation 

ANSWER: Starter for a car

Explanation:
No explanation is available for this question!


9)   In D.C. machines fractional pitch winding is used__________?

a. to improve cooling
b. to reduce copper losses
c. to increase the generated e.m.f.
d. to reduce the sparking
Answer  Explanation 

ANSWER: to reduce the sparking

Explanation:
No explanation is available for this question!


10)   A three point starter is considered suitable for______________?

a. shunt motors
b. shunt as well as compound motors
c. shunt, compound and series motors
d. all D.C. motors
Answer  Explanation 

ANSWER: shunt as well as compound motors

Explanation:
No explanation is available for this question!


11)   In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?

a. 100%
b. around 90%
c. anywhere between 75% and 90%
d. less than 50%
Answer  Explanation 

ANSWER: less than 50%

Explanation:
No explanation is available for this question!


12)   The ratio of starting torque to full-load torque is least in case of____________?

a. series motors
b. shunt motors
c. compound motors
d. none of the above
Answer  Explanation 

ANSWER: shunt motors

Explanation:
No explanation is available for this question!


13)   In D.C. motor which of the following can sustain the maximum temperature rise?

a. Slip rings
b. Commutator
c. Field winding
d. Armature winding
Answer  Explanation 

ANSWER: Field winding

Explanation:
No explanation is available for this question!


14)   Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?

a. Lenz’s law
b. Faraday’s law
c. Coloumb’s law
d. Fleming’s left-hand rule
Answer  Explanation 

ANSWER: Fleming’s left-hand rule

Explanation:
No explanation is available for this question!


15)   Which of the following load normally needs starting torque more than the rated torque?

a. Blowers
b. Conveyors
c. Air compressors
d. Centrifugal pumps
Answer  Explanation 

ANSWER: Conveyors

Explanation:
No explanation is available for this question!


16)   The starting resistance of a D.C. motor is generally_______________?

a. low
b. around 500 Q
c. 1000 Q
d. infinitely large
Answer  Explanation 

ANSWER: low

Explanation:
No explanation is available for this question!


17)   The speed of a D.C. series motor is_____________?

a. proportional to the armature current
b. proportional to the square of the armature current
c. proportional to field current
d. inversely proportional to the armature current
Answer  Explanation 

ANSWER: inversely proportional to the armature current

Explanation:
No explanation is available for this question!


18)   In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to

a. 100% of the previous value
b. 50% of the previous value
c. 25% of the previous value
d. 10% of the previous value
e. none of the above
Answer  Explanation 

ANSWER: 25% of the previous value

Explanation:
No explanation is available for this question!


19)   The current drawn by the armature of D.C. motor is directly proportional to__________?

a. the torque required
b. the speed of the motor
c. the voltage across the terminals
d. none of the above
Answer  Explanation 

ANSWER: the torque required

Explanation:
No explanation is available for this question!


20)   The power mentioned on the name plate of an electric motor indicates____________?

a. the power drawn in kW
b. the power drawn in kVA
c. the gross power
d. the output power available at the shaft
Answer  Explanation 

ANSWER: the output power available at the shaft

Explanation:
No explanation is available for this question!