D.C. Motors MCQ Practice Test - Set 02

Practice Test: Question Set - 02


1. For which types of D.C. motor, dynamic braking is generally used?
    (A) Shunt motors
    (B) Series motors
    (C) Compound motors
    (D) All of the above

2. 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
    (A) Series motor
    (B) Shunt motor
    (C) Compound motor
    (D) Any of the above

3. One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven
    (A) Runs as a generator
    (B) Does not run as a generator
    (C) Also runs as a motor comes to stop after sometime
    (D) None of these

4. The direction of rotation of a D.C. series motor can be changed by
    (A) Interchanging supply terminals
    (B) Interchanging field terminals
    (C) Either of (A) and (B) above
    (D) None of the above

5. A D.C. series motor is that which
    (A) Has its field winding consisting of thick wire and less turns
    (B) Has a poor torque
    (C) Can be started easily without load
    (D) Has almost constant speed

6. 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

7. Which of the following load normally needs starting torque more than the rated torque?
    (A) Blowers
    (B) Conveyors
    (C) Air compressors
    (D) Centrifugal pumps

8. Which one of the following is not the function of pole shoes in a D.C. machine?
    (A) To reduce eddy current loss
    (B) To support the field coils
    (C) To spread out flux for better uniformity
    (D) To reduce the reluctance of the magnetic path

9. Speed control by Ward Leonard method gives uniform speed variation
    (A) In one direction
    (B) In both directions
    (C) Below normal speed only
    (D) Above normal speed only

10. As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit
    (A) A resistance is connected in series with armature
    (B) A resistance is connected parallel to the armature
    (C) Armature is temporarily open circuited
    (D) A high value resistor is connected across the field winding

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