1. A direct on line starter is used: for starting motors
(a) iip to 5 H.P.
(b) up to 10 H.P.
(c) up to 15 H.P.
(d) up to 20 H.P.
Ans: (a) iip to 5 H.P.
2. 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
Ans: (d) more than full-load current
3. The ratio of starting torque to full-load torque is least in case of
(a) series motors
(b) compound motors
(c) shunt motors
(d) none of the above
Ans: (c) shunt motors
4. The starting resistance of a D.C. motor is generally
(a) low
(b) around 500 Q
(c) 1000 Q
(d) infinitely large
Ans: (a) low
Ans:(c) differentially compounded
6. In D.C. motor which of the following can sustain the maximum temperature rise?
(a) Field winding
(b) Commutator
(c) Slip rings
(d) Armature winding
Ans: (a) Field winding
7. The speed of a D.C. shunt motor more than its full-load speed can be obtained by
(a) decreasing the field current
(b) increasing the field current
(c) decreasing the armature current
(d) increasing the armature current
Ans: (a) decreasing the field current
8. 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
Ans: (c) The armature may burn
9. In a D.C. shunt motor, speed is
(a) inversely proportional to the armature current
(b) directly proportional to the armature current
(c) proportional to the square of the current
(d) independent of armature current
Ans: (d) independent of armature current
10. 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
Ans: (d) Fleming's left-hand rule
(a) Blowers
(b) Conveyors
(c) Air compressors
(d) Centrifugal pumps
Ans:(b) Conveyors
(a) iip to 5 H.P.
(b) up to 10 H.P.
(c) up to 15 H.P.
(d) up to 20 H.P.
Ans: (a) iip to 5 H.P.
2. 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
Ans: (d) more than full-load current
3. The ratio of starting torque to full-load torque is least in case of
(a) series motors
(b) compound motors
(c) shunt motors
(d) none of the above
Ans: (c) shunt motors
4. The starting resistance of a D.C. motor is generally
(a) low
(b) around 500 Q
(c) 1000 Q
(d) infinitely large
Ans: (a) low
5. For the same H.P. rating and full load speed, following motor has poor starting torque
(a) shunt
(b) series
(c) differentially compounded
(d) cumulativelyc'ompounded
6. In D.C. motor which of the following can sustain the maximum temperature rise?
(a) Field winding
(b) Commutator
(c) Slip rings
(d) Armature winding
Ans: (a) Field winding
7. The speed of a D.C. shunt motor more than its full-load speed can be obtained by
(a) decreasing the field current
(b) increasing the field current
(c) decreasing the armature current
(d) increasing the armature current
Ans: (a) decreasing the field current
8. 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
Ans: (c) The armature may burn
9. In a D.C. shunt motor, speed is
(a) inversely proportional to the armature current
(b) directly proportional to the armature current
(c) proportional to the square of the current
(d) independent of armature current
Ans: (d) independent of armature current
10. 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
Ans: (d) Fleming's left-hand rule
11. D.C. series motors are used
(a) where load is constant
(b) in none of the above situations.
(c) where constant operating speed is needed
(d) where load changes frequently
Ans: (b) in none of the above situations.
12. Which of the following motor is preferred for operation in highly explosive
atmosphere ?
(a) Air motor
(b) Shunt motor
(c) Series motor
(d) Battery operated motor
Ans: (a) Air motor
13. Which of the following load normally needs starting torque more than the rated
torque?(a) Blowers
(b) Conveyors
(c) Air compressors
(d) Centrifugal pumps
Ans:(b) Conveyors
14. In case of conductively compensated D.C. series motors, the compensating winding is
provided
(a) as separately wound unit
(b) in series with armature winding
(c) in parallel with field winding
(d) in parallel with armature winding
Ans: (b) in series with armature winding
15. 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
Ans: (d) flux is practically constant in D:C. shunt motors
(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
Ans: (d) flux is practically constant in D:C. shunt motors
16. Sparking at the commutator of a D.C. motor may result in
(a) damage to commutator segments
(b) damage to commutator insulation
(c) increased power consumption
(d) all of the above
Ans: (d) all of the above
17. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
(a) nothing will happen to the motor
(b) this will make armature to take heavy current, possibly burning it
(c) motor will run at very slow speed
(d) this will result in excessive speed, possibly destroying armature due to excessive
centrifugal stresses
Ans: (d) this will result in excessive speed, possibly destroying armature due to excessive
centrifugal stresses
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