Electrical DC Motors Multiple Choice Questions- Set 07 - ObjectiveBooks

Electrical DC Motors Multiple Choice Questions- Set 07

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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