D.c. Motors(Electrical Engineering ) Questions and Answers

Question 1. The condition for maximum efficiency for a D.C. generator is
  1.    Eddy current losses = stray losses
  2.    Hysteresis losses = eddy current losses
  3.    Copper losses = 0
  4.    Variable losses = constant losses
Explanation:-
Answer: Option D. -> Variable losses = constant losses
Question 2. The armature voltage control of D.C. motor provides
  1.    Constant torque drive
  2.    Constant voltage drive
  3.    Constant current drive
  4.    None of the above
Explanation:-
Answer: Option A. -> Constant torque drive
Question 3. If a D.C. motor is connected across the A.C. supply it will
  1.    Run at normal speed
  2.    Not run
  3.    Run at lower speed
  4.    Burn due to heat produced in the field winding by eddy currents
Explanation:-
Answer: Option D. -> Burn due to heat produced in the field winding by eddy currents
Question 4. The speed of a D.C. shunt motor can be increased by
  1.    Increasing the resistance in armature circuit
  2.    Increasing the resistance in field circuit
  3.    Reducing the resistance in the field circuit
  4.    Reducing the resistance in the armature circuit
Explanation:-
Answer: Option B. -> Increasing the resistance in field circuit
Question 5. Starters are used with D.C. motors because
  1.    These motors have high starting torque
  2.    These motors are not self-starting
  3.    Back e.m.f. of these motors is zero initially
  4.    To restrict armature current as there is no back e.m.f. while starting
Explanation:-
Answer: Option D. -> To restrict armature current as there is no back e.m.f. while starting
Question 6. In D.C. machines the residual magnetism is of the order of
  1.    2 to 3 percent
  2.    10 to 15 percent
  3.    20 to 25 percent
  4.    50 to 75 percent
Explanation:-
Answer: Option A. -> 2 to 3 percent
Question 7. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
  1.    Frame
  2.    Shaft
  3.    Commutator
  4.    Stator
Explanation:-
Answer: Option C. -> Commutator
Question 8. For constant torque drive which speed control method is preferred?
  1.    Field control
  2.    Armature voltage control
  3.    Shunt armature control
  4.    Mechanical loading system
Explanation:-
Answer: Option B. -> Armature voltage control
Question 9. In a D.C. generator, the iron losses mainly take place in
  1.    Yoke
  2.    Commutator
  3.    Armature conductors
  4.    Armature rotor
Explanation:-
Answer: Option D. -> Armature rotor
Question 10. Which D.C. motor has got maximum self loading property?
  1.    Series motor
  2.    Shunt motor
  3.    Cumulatively compounded motor
  4.    Differentially compounded motor
Explanation:-
Answer: Option D. -> Differentially compounded motor
© Lakshya_Education.com, All Right Reserved.
Contact Us services