Question: In variable speed motor___________?
- 1. a stronger commutating field is needed at low speed than at high speed
- 2. a weaker commutating field is needed at low speed than at high speed
- 3. same commutating field is needed at low speed than at high speed
- 4. none of the above is correct
Question: When the armature of a D.C. motor rotates, e.m.f. induced is___________?
- 1. self-induced e.m.f.
- 2. mutually induced e.m.f.
- 3. back e.m.f
- 4. none of the above
Question: Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?
- 1. drum type controller is used
- 2. three point starter is used
- 3. four point starter is used
- 4. all above can be used
Question: If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?
- 1. this will make armature to take heavy current, possibly burning it
- 2. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
- 3. nothing will happen to motor
- 4. motor will come to stop
Question: D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?
- 1. series motor
- 2. shunt motor
- 3. compound motor
- 4. any of the above
Question: D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this______________?
- 1. series motor
- 2. shunt motor
- 3. compound motor
- 4. any of the above
Question: Which D.C. motor has got maximum self relieving property ?
- 1. Series motor
- 2. Shunt motor
- 3. Cumulatively compounded motor
- 4. Differentially compounded motor
Question: In the D.C. motor the iron losses occur in____________?
- 1. the field
- 2. the armature
- 3. the brushes
- 4. the commutator
Question: The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by______________?
- 1. reducing the field current
- 2. decreasing the armature current
- 3. increasing the armature current
- 4. increasing the excitation current
Question: If the load on a DC shunt motor is increases, its speed is slightly reduced due to______________?
- 1. increase in armature current
- 2. increase in flux
- 3. decrease in reactance
- 4. decrease in back emf
