MCQ Qestions for SSC JE Electrical

27. The effective value of voltage given by V = 100 + 25 sin 3wt + 10 sin 5wt will be

(a) 100 V
(b) 101.8 V
(c) 110 V
(d) 135 V

28. The voltage V and current i of a device are V = 100 sin 377t, i = 10 sin (377 t + 30°) The power P indicated by wattmeter will be

(a) 1000 W
(b) 774 W
(c) 500 W
(d) 433 W

29. Zero power factor method for an alternator is generally used to determine

(a) efficiency of alternator
(b) synchronous impedance of alternator
(c) voltage regulation of alternator
(d) all of the above

30. Two alternators A and B are sharing the inductive load equally. What will happen when the excitation of A is increased?

(a) Current delivered by A will increase and B will decrease
(b) Current of A will decrease & B will increase
(c) Both will continuous to share the load equally
(d) None of the above

31. The percentage slip in case of synchronous motor is

(a) 1%
 (b) 100%
(c) 0.5%
(d) zero

32. Torque angle of synchronous motor is

(a) Angle through which motor lags behind synchronous speed
(b) Angle of lag from no load to full load
(c) Angle between rotating stator flux and rotor poles
(d) None of the above

33. Which of the following is preferren rpm for 4-pole induction motor ?

(a) 1485 rpm
(b) 1470 rpm
(c) 1440 rpm
(d) 1320 rpm

34. Maximum torque in a 3-phase induction motor depends on

(a) Square of supply voltage
(b) Frequency
(c) Rotor inductive reactance
(d) All of the above

35. Full load, current for a 3-phase 440 Volt, 20 Hp induction motor will be closer to

(a) 5A
(b) 15A
(c) 25A
(d) 35A

36. How many different speeds can be obtained in cascade control of two induction motor?

(a) 2
(b) 4
(c) 8
(d) 16

Answer: (b) 4

37. A universal motor can be operated on 220V D.C. as well as 220 V single-phase A.C. Which of the following will be same in the two cases ?

(a) operating speed
(b) power output
(c) operating speed and power output
(d) none fo the above

38. A transformer has maximum efficiency at full load, when iron losses are 800 watts. Copper losses at half load will be

(a) 1600W
(b) 800W
(c) 400W
(d) 200W

39. Which of the following is not a standard transmission voltage in India ?

(a) 33kV
(b) 66kV
(c) 99kV
(d) 220kV

40. A load power factor of 0.95 lagging implies reactive power demand of

(a) 0.05 kVAR per kW
(b) 0.10 kVAR per kW
(c) 0.33 kVAR per kW
(d) 0.95 kVAR per kW

Answer: (c) 0.33 kVAR per kW

41. Which of the following processes essentially needs direct current ?

(a) Welding
(b) Heating
(c) Refrigeration
(d) Electroplating

42. The power factor of a spot welding machine is expected to be around

(a) 0.3 to 0.5 leading
(b) unity
(c) 0.8 lagging
(d) 0.3 to 0.5 lagging

43. In helium arc welding the electrode is made of

(a) copper
(b) carbon
(c) mild steel
(d) tungsten

44. A dynamometer type wattmeter can be used on

(a) DC only
(b) AC only
(c) Rectified AC only
(d) AC as well as DC

45. Which of the following instruments is an integrating type instrument ?

(a) Wattmeter
(b) Energy meter
(c) Power factor meter
(d) None of the above

46. Which of the following A.C. bridges is preferred for the measurement of inductance having high Q-factor ?

(a) Hays bridge
(b) Maxwell bridge
(c) Desauty bridge
(d) Wien bridge

47. Two D.C. series motors are connected in series to produce a torque T. Now if the motors are connected in parallel, the torque produced will be

(a) T/4
(b) T/2
(c) 2T
(d) 4T

Answer: (a) T/4

48. Which motor has the poorest speed control ?

(a) Differentially compound motor
(b) Comulatively compound motor
(c) Shunt motor
(d) Series motor

49. Which D.C. motor is generally preferred for cranes and hoists ?

(a) Series motor
(b) Shunt motor
(c) Cumulatively compound motor
(d) Differentially compound motor

50. The unit of luminous flux is

(a) watt
(b) watt/m2
(c) lumen
(d) lumen/m2

51. If the fault current is 2000 amp, the relay setting at 50% and CT ratio is 400/5, then the plug setting multiplier will be

(a) 25amp
(b) 15amp
(c) 50amp
(d) None of the above

Answer: (d) None of the above