MCQ
41. Inductance opposes --in current in a circuit.
ব্যাখ্যা : According to Lenz's law, the induced voltage has a polarity (direction) which opposes the change in current that created it. As a result, inductors oppose any changes in current.
only increase
change
only decrease
none of the above
42. At parallel resonance-
circuit impedance is minimum
power factor is zero
line current is maximum
power factor is unity
43. The average value of a sinusoidal current is 100A. Its rms value is-
70.7A
63.7A
141.4A
111A
44. যদি Delta সার্কিটে একটি phase open করা হয় তাহলে Total power এর কত অংশ কমবে?
1/3 অংশ
1/2 অংশ
2 অংশ
কোনোটিই নয়
45. The capacitive reactance of a circuit is-frequency.
independent of
inversely proportional to
directly proportional to
none of the above
46. For Y-connection under balanced condition the line to line voltage is-
same as the phase voltage
√3 times the phase voltage
√2 times the phase voltage
none of the above
47. What is the power frequency (Hz) of Bangladesh?
30
60
50
None
48. The phase sequence of a three-phase system is RYB. The other possible phase sequence can be-
BRY
YRB
RBY
none of the above
49. At parallel resonance the circuit impedance equals to-
L/CR
LC/R
RL/C
CR/L
50. Which of the following connections is best suited for 3-phase, 4-wire service?
ব্যাখ্যা: Δ-Υ connection is popular for both the step (transmission side, high voltage) and step-down (distribution zide, low voltage) applications
Δ-Δ
Y-Y
Δ-Υ
Y-A
51. The unit of inductance—
Inducta
henry
inductive reactance
ohm
52. Two identical capacitors are connected in parallel and charged to a potential of V. They are separated and then connected in series. The potential across the series combination is-
V
3V
4V
2V
53. If a phase is multiplied by j, then –
ব্যাখ্যা: It we multiplied by then the phase direction will rotate through a fixed angle of 90° in an anticlockwise direction. In each successive rotation, the magnitude of the vector always remains the same.
only its magnitude changes
only its direction changes
both magnitude & direction changes.
none of above
54. RMS value of the instantaneous ac voltage V = 300 is-
300x√2
300/√2
300x√3
300/√3
55. Which of the following lamp has minimum initial cost of installation but maximum running cost?
ব্যাখ্যা: Incandescent lamp has higher resistance compare to other lamps. As a result more electricity is used to run this blubs. So the running cost is high.
incandescent
fluorescent
mercury vapour
sodium vapour
56. একটি Heater 230/250 voltage-এ উত্তপ্ত হয়। যখন 250 volt সরবরাহ পায় তখন 5 Amp বিদ্যুৎ প্রবাহিত হয়, তবে যখন 230 volt সরবরাহ পায় তখন কত বিদ্যুৎ প্রবাহিত হবে?
3.6
5.6
4.6
কোনোটিই নয়
57. Inductance opposes --in current in a circuit
ব্যাখ্যা : According to Lenz's law, the induced voltage has a polarity (direction) which opposes the change in current that created it. As a result, inductors oppose any changes in current.
only increase
change
only decrease
none of the above
58. Four capacitors each of 40µF are connected in parallel, the equivalent capacitance will be-
160µF
40µF
10µF
5µF
59. In a series R.L circuit, voltage across resistor inductor are 3V and 4V respectively, then what is the applied voltage?
7V
4V
5V
3V
60. What is the peak-to-peak value for 120V ac?
240V
339V
480V
391V