electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
5601. Starters are used with D.C. motors because______________?
comments icon0

A. back e.m.f. of these motors is zero initially

B. these motors have high starting torque

C. to restrict armature current as there is no back e.m.f. while starting

D. these motors are not self-starting

5602. In D.C. shunt motors as load is reduced__________________?
comments icon0
A. the speed will remain almost/constant

B. the speed will reduce

C. the speed will increase abruptly

D. the speed will increase in proportion to reduction in load

5603. D.C. series motors are used______________?
comments icon0

A. where load changes frequently

B. where constant operating speed is needed

C. where load is constant

D. in none of the above situations
5604. The main disadvantage of the Ward-Leonard control method is______________?
comments icon0
A. all of the above

B. high maintenance cost

C. low efficiency at Hght loads

D. high initial cost

5605. If the field winding resistance of a DC shunt motor is increases, its speed will____________?
comments icon0
A. increases

B. none of the above

C. the field winding resistance of a DC shunt motor is increases, its speed will

D. remains same

E. decreases

5606. Which one of the following is not the function of pole shoes in a D.C. machine ?
comments icon0
A. To reduce eddy current loss

B. To reduce the reluctance of the magnetic path

C. To spread out flux for better uniformity

D. To support the field coils

5607. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?
comments icon0

A. around 90%

B. anywhere between 75% and 90%

C. less than 50%

D. 100%

5608. Regenerative method of braking is based on that___________?
comments icon0

A. none of the above

B. back e.m.f. of rotor is more than the applied voltage

C. back e.m.f. is less than the applied voltage

D. back e.m.f. is equal to the applied voltage
5609. Hopkinsons test on D.C. machines is conducted at_______________?
comments icon0

A. no-load

B. full-load

C. part load

D. overload

5610. Which of the following test can be performed on DC series motor?
comments icon0
A. Field test

B. Hopkinson test

C. Swinburne test

D. Brake test

5611. Which of the following loss in a D.C. generator is dissipated in the form of heat?
comments icon0

A. Core loss

B. Mechanical loss

C. All of the above

D. Copper loss

5612. In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
comments icon0

A. none of the above

B. 10% of the previous value

C. 100% of the previous value

D. 50% of the previous value

E. 25% of the previous value
5613. The speed of a D.C. series motor is_____________?
comments icon0

A. proportional to the armature current

B. proportional to field current

C. inversely proportional to the armature current

D. proportional to the square of the armature current

5614. Torque developed by a D.C. motor depends upon_____________?
comments icon0

A. current flow through the conductors

B. radius of armature

C. magnetic field

D. active length of the conductor

E. all above factors

F. number of conductors

5615. The armature torque of the D.C. shunt motor is proportional to____________?
comments icon0

A. field flux only

B. armature current only

C. both A. and B.

D. none of the above

5616. Which D.C. motor is generally preferred for cranes and hoists ?
comments icon0

A. Shunt motor

B. Series motor

C. Differentially compounded motor

D. Cumulatively compounded motor

5617. A dc series motor should not be started on no load because it would___________?
comments icon0

A. draw more current without producing sufficient torque

B. run at dangerously high speed

C. not develop starting torque

D. fail to start without load

5618. In D.C. machines the residual magnetism is of the order of_________________?
comments icon0

A. 10 to 15 per cent

B. 20 to 25 per cent

C. 50 to 75 per cent

D. 2 to 3 per cent
5619. In a DC motor the inter-pole winding is connected in________________?
comments icon0

A. parallel big field winding

B. parallel with armature winding

C. series with field winding

D. series speed armature winding
5620. For which of the following applications a D.C. motor is preferred over an A.C. motor ?
comments icon0

A. High speed operation

B. Low speed operation

C. Variable speed operation

D. Fixed speed operation

5621. If a D.C. motor designed for 40C ambient temperature is to be used for 50C ambient temperature, then the motor_____________?
comments icon0
A. is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor

B. can be used for 50C ambient temperature also

C. of higher H.P. should be selected

D. of lower H.P. should be selected

5622. In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be_____________?
comments icon0
A. more than full-load current

B. less than full-load current

C. almost negligible

D. rated full-load current

5623. Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
comments icon0

A. Hopkinsons test

B. Brake test

C. Swinburnes test

D. Field test
5624. The total losses in a well designed D.C. generator of 10 kW will be nearly______________?
comments icon0
A. 500 W

B. 1000 W

C. 1500 W

D. 100 W

5625. Which of the following motor is preferred for operation in highly explosive atmosphere ?
comments icon0

A. Series motor

B. Shunt motor

C. Air motor

D. Battery operated motor

5626. Which of the following motors is usually used in house-hold refrigerators ?
comments icon0

A. Reluctance motor

B. D.C. series motor

C. D.C. shunt motor

D. Single phase induction motor (split phase start or induction run motor)

E. Synchronous motor

5627. Speed control by Ward Leonard method gives uniform speed variation_____________?
comments icon0

A. in one direction

B. in both directions

C. below normal speed only

D. above normal speed only

5628. In Ward-Leonard control the lower limit of speed is imposed by________?
comments icon0

A. mechanical losses of motor and generator together

B. residual magnetism of the generator

C. all of the above

D. core losses of motor

5629. Which of the following load normally needs starting torque more than the rated torque?
comments icon0

A. Air compressors

B. Centrifugal pumps

C. Conveyors

D. Blowers

5630. In a D.C. generator, the iron losses mainly take place in___________/
comments icon0

A. armature conductors

B. armature rotor

C. commutator

D. yoke

5631. The speed of a D.C. shunt motor more than its full-load speed can be obtained by_____________?
comments icon0

A. increasing the field current

B. increasing the armature current

C. decreasing the field current

D. decreasing the armature current

5632. Which motor has the poorest speed control?
comments icon0

A. Differentially compounded motor

B. Cumulatively compounded motor

C. Shunt motor

D. Series motor
5633. With the increase in temperature, the speed of DC series motor______________?
comments icon0
A. decreases

B. remain same

C. none of the above

D. increases

5634. Armature reaction in dc motor results___________?
comments icon0

A. open circuit

B. decrease in speed

C. short circuit

D. increase in speed
5635. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
comments icon0

A. Using non-magnetic material for frame

B. Using material of low hysteresis co-efficient for armature core material

C. Providing laminations in stator

D. Providing laminations in armature core

5636. For a D.C. shunt motor if the excitation is changed_______________?
comments icon0

A. torque will remain constant

B. torque will change but power will remain constant

C. torque and power both will change

D. torque, power and speed, all will change

5637. The current drawn by the armature of D.C. motor is directly proportional to__________?
comments icon0

A. the voltage across the terminals

B. the torque required

C. the speed of the motor

D. none of the above

5638. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________?
comments icon0
A. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses D. motor will run at very slow speed

B. this will make armature to take heavy current, possibly burning it

C. nothing will happen to the motor

5639. A direct on line starter is used: for starting motors___________?
comments icon0

A. up to 20 H.P

B. up to 15 H.P

C. up to 5 H.P

D. up to 10 H.P

5640. In the D.C. motor the iron losses occur in____________?
comments icon0

A. the brushes

B. the armature

C. the field

D. the commutator

5641. Which motor should not be started on no-load ?
comments icon0

A. Cumulatively compounded motor

B. Series motor

C. Shunt motor

D. Differentially compounded motor

5642. If I2 be the armature current, then speed of a D.C. shunt motor is_______________?
comments icon0

A. varies as (Ia)

B. proportional to la

C. independent of Ia

D. varies as la

5643. Which D.C. motor has got maximum self relieving property ?
comments icon0
A. Series motor

B. Shunt motor

C. Cumulatively compounded motor

D. Differentially compounded motor

5644. In a manual shunt motor starter?
comments icon0
A. over load relay is connected in series and no volt relay in parallel with the load

B. over load relay is connected in parallel and no volt relay in series with the load

C. over load relay and no volt relay are both connected in series with the load

D. over load relay and no volt relay are both connected in parallel with the load

5645. The purpose of retardation test on D.C. shunt machines is to find out____________?
comments icon0

A. eddy current losses

B. stray losses

C. field copper losses

D. windage losses

5646. Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?
comments icon0

A. four point starter is used

B. three point starter is used

C. drum type controller is used

D. all above can be used

5647. With the increase in temperature, the speed of DC shunt motor____________?
comments icon0

A. decreases.

B. remain same

C. increases

D. none of the above

5648. For which types of D.C. motor, dynamic braking is generally used ?
comments icon0

A. Shunt motors

B. All of the above

C. Compound motors

D. Series motors

5649. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?
comments icon0

A. Coloumbs law

B. Lenzs law

C. Faradays law

D. Flemings left-hand rule
5650. 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____________________?
comments icon0

A. a resistance is connected parallel to the armature

B. a high value resistor is connected across the field winding

C. a resistance is connected in series with armature

D. armature is temporarily open circuited