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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