DC motor mcq questions answers part1

Q1. Suppose we are connecting DC motor across ac supply. The motor
(A) will not run
(B) will run at normal speed
(C) will run at lower speed
(D) damaged due to heat produced in the field winding by eddy currents

Q2. In DC shunt motors as load is reduced
(A) the speed will reduce
(B) the speed will increase abruptly
(C) the speed will remain constant
(D) the speed will increase in proportion

Q3. DC motors are widely used in
(A) electric traction
(B) pumping sets
(C) air compressors
(D) machine shops

Q4. DC motor speed can be varied by varying
(A) applied voltage
(B) field current
(C) resistance in series with armature
(D) any of these

Q5. Which of the following D.C. motors is preferred for elevators?
(A) Series motor
(B) Shunt motor
(C) Cumulative compound motor
(D) Differentiate compound motor

Q6. Torque developed by a D.C. motor depends upon
(A) current flow through the conductors
(B) number of conductors
(C) magnetic field
(D) all of these

Q7. If the field of a D.C. shunt motor gets opened while motor is running
(A) armature current will reduce
(B) speed of motor will be reduced
(C) motor will run at dangerously high speed
(D) None of these

Q8. A DC motor is preferred over an AC motor for :
(A) High speed operation
(B) Variable speed operation
(C) Low speed operation
(D) Fixed speed operation

Q9. A three point starter is suitable for
(A) shunt motors
(B) compound motors
(C) shunt as well as compound motors
(D) shunt, compound and series motors

Q10. How can we change the direction of rotation of a D.C. series motor?
(A) interchanging supply terminals
(B) interchanging field terminals
(C) Either by interchanging supply terminals or by interchanging field terminals
(D) None of these

Q11. Which of the following is correct regarding DC shunt motor?
(A) speed proportional to the square of the current
(B) speed is independent of armature current
(C) speed is directly proportional to the armature current
(D) speed is inversely proportional to the armature current

Q12. Which of the following law can he used to determine the direction of rotation of a motor ?
(A) Coloumbs law
(B) Faradays law
(C) Lenzs law
(D) Flemings left-hand rule

Q13. Which of the following D.C. motor will be preferred for machine tools?
(A) Series motor
(B) Shunt motor
(C) Cumulative compound motor
(D) Differentiate compound motor

Q14. Which of the following motor is used when high starting torque and wide speed range control is required:
(A) DC motor
(B) Induction motor
(C) Synchronous motor
(D) Single phase capacitor start

Q15. The use of starter in a DC motor is to:
(A) limits the speed of the motor
(B) limits the starting current to a safe value
(C) Both of these
(D) None of these

Q16. Maximum efficiency for a D.C. generator is when,
(A) copper losses zero
(B) eddy current losses equals stray losses
(C) hysteresis losses equals eddy current losses
(D) variable losses equals constant losses

Q17. Differentially compound D.C. motors used in applications which requires
(A) low starting torque
(B) high starting torque
(C) variable speed
(D) frequent on-off cycles

Q18. The resultant speed, When two D.C. series motors are connected in parallel is
(A) zero
(B) normal speed
(C) less than the normal speed
(D) more than the normal speed

Q19. The ratio of starting torque to full load torque is least for
(A) series motors
(B) shunt motors
(C) compound motors
(D) None of these

Q20. Which of the following motors has the highest no load speed?
(A) Series motor
(B) Shunt motor
(C) Cumulative compound motor
(D) Differentiate compound motor