SSC JE Electrical MCQ Questions

26. Dielectric heating is also called

(a) Volume heating
(b) infrared heating
(c) surface heating
(d) eddy current heating

27. Voltage drop is the main consideration while designing a

(a) Feeder
(b) Distributor
(c) Service main
(d) All the above

28. Laboratory wattmeters are

(a) Induction type
(b) Moving iron type
(c) Electrostatic type
(d) Electro-dynamometer type

29. An electric motor may give noise due to

(a) magnetic effect
(b) defective bearing
(c) cooling air
(d) all the above

30. Which of the following motor is used in household refrigeration?

(a) Synchronous motor
(b) D.C. shunt motor
(c) 3-phase induction motor
(d) 1-phase induction motor

31. The lighting arrester is connected

(a) in series with the line
(b) between line and earth
(c) to a pole near the line
(d) to circuit breaker

32. If R_g in the circuit shown in figure is variable between 20 ohm and 80 ohm then maximum power transferred to the load R_L will be

(a) 15 ohm
(b) 13.33 ohm
(c) 6.67 ohm
(d) 2.4 ohm

33. The knowledge of diversity factor helps in computing

(a) plant capacity
(b) average load
(c) units generator
(d) peak density

34. Distribution transformers are designed to have maximum efficiency nearly at

(a) 100% of full load
(b) 50% of full load
(c) 25% of full load
(d) 10% of full load

35. Electronic switching are becoming more and more popular because of

(a) noiseless operation
(b) long life
(c) smaller size and weight
(d) all the above

36. The controlling torque in gravity controlled meter is proportional to

(a) cos θ
(b) sin θ
(c) tan θ
(d) θ

37. The condition for a maximum power output from dc motor is

(a) E_b = V
(b) E_b = V/2
(c) E_b = 0
(d) E_b = V/√2

38. Time constant of th network shown in figure is

(a) 2 RC
(b) 3 RC
(c) RC/2
(d) 2RC/3

39. A 2 kVA transformer has iron loss of 150 W and full load copper loss of 250 W. The maximum efficiency of the transformer will occur when the total loss is

(a) 500 W
(b) 400 W
(c) 300 W
(d) 275 W

40. While starting synchronous motor its field winding should be

(a) kept open
(b) connected to a dc source
(c) connected to ac source
(d) kept short-circuited

41. A 4-pole, 3-phase induction motor is running at 4% slip at full load. If the speed of the motor is 750 rpm, the supply frequency is

(a) 16 x 2/3 Hz
(b) 25 Hz
(c) 50 Hz
(d) 60 Hz

42. An oscillator uses

(a) Positive feedback
(b) Negative feedback
(c) Both positive and negative feedback
(d) No feedback

43. Permeans is analogous to

(a) Conductance
(b) Reluctance
(c) Inductance
(d) Resistance

44. A wire has a resistance 10 ohms. It is stretched by one-tenth of its original length. Then its resistance will be

(a) 10 ohms
(b) 12.1 ohms
(c) 9 ohms
(d) 11 ohms

45. Potential transformer are used

(a) to measure high a.c. voltage
(b) to measure high d.c. voltage
(c) both (a) and (b)
(d) as protective device in high voltage circuits

46. To increase the range of a voltmeter

(a) a low resistance is connected in series
(b) a low resistance is connected in parallel
(c) a high resistance is connected in series
(d) a high resistance is connected in parallel

47. A three phase power transformer is provided with star-delta connections. In order to protect angainst fault, connection for current transformer should be in

(a) Star-star
(b) Delta-star
(c) Delta-delta
(d) Star-delta

48. For active region operation of NPN transistor

(a) Emitter is positive with respect to base
(b) Emitter is –ve with respect to base
(c) Emitter is at same voltage as base
(d) base is at same voltage as collector

49. The advatage of electric breaking is

(a) It is instantaneous
(b) More heat is generated during breaking
(c) it avoids wear of track
(d) Motor continue to remain load druing breaking

50. A single phase motor is made-starting by the addition of a / an

(a) Running winding
(b) Starting winding
(c) Electric starter
(d) Autotransformer