Practice Test: Question Set - 07
1. Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be
- (A) Level compounded
- (B) Under compounded
- (C) Cumulatively compounded
- (D) Differentially compounded
2. If I2 be the armature current, then speed of a D.C. shunt motor is
- (A) Independent of Ia
- (B) Proportional to Ia
- (C) Varies as Ia
- (D) None of these
3. Why are the D.C. motors preferred for traction applications?
- (A) Torque and speed are inversely proportional to
armature current
- (B) Torque is proportional to armature current
- (C) Torque is proportional to square root of armature
current
- (D) The speed is inversely proportional to the torque
and the torque is proportional to square of armature current
4. Which of the following loss in a D.C. generator is dissipated in the form of heat?
- (A) Mechanical loss
- (B) Core loss
- (C) Copper loss
- (D) All of the above
5. Which method of braking is generally used in elevators?
- (A) Plugging
- (B) Regenerative braking
- (C) Rheostat braking
- (D) None of the above
6. In the D.C. motor the iron losses occur in
- (A) The field
- (B) The armature
- (C) The brushes
- (D) The commutator
7. Which D.C. motor will be preferred for machine tools?
- (A) Series motor
- (B) Shunt motor
- (C) Cumulative compound motor
- (D) Differential compound motor
8. If a D.C. motor is connected across the A.C. supply it will
- (A) Run at normal speed
- (B) Not run
- (C) Run at lower speed
- (D) Burn due to heat produced in the field winding by eddy
currents
9. These days D.C. motors are widely used in
- (A) Pumping sets
- (B) Air compressors
- (C) Electric traction
- (D) Machine shops
10. 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
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