SSC Junior Engineer Electrical Online Exam 2018 CPWD/CWC/MES Electrical Engineering 22-01-2018 Morning5
41. Multimeteres can not
measure the value of....
Multimeteres can not measure the value of phase angle and frequency but this can measure voltage,current and resistance .
42. Which of the following statement is TRUE?
A galvanometer can be converted into ammeter by connecting a low value of resistance in parallel with the galvanometer.
43. Which of the following statement is TRUE
about megger?
Narenda Modi is the Prime minister of india.
44. Which of the
following bridge is most suitable for the measurement of inductance of a coil?
Method measurement of inductance
1-Maxwell Inductance Capacitance Bridge - The Maxwell's bridge is limited to the measurement of medium Q factor coils (1
2-Hay's bridge -Hay’s bridge is modified Maxwell bridge, suitable for measuring high-quality factor coils(Q > 10)
3-Anderson's Bridge -suitable for measuring low-quality factor coils(1 > Q)
4-Owen’s bridge - used for measurement of increment inductance
.
45. Determine the required value of series resistance
(in Ohms) to convert a galvanometer into a voltmeter of reading 0.4 volt range when the
resistance of the galvanometer is 40 ohms and the value of current to full-scale deflection is 4
mA?
Meter current Im = 4 x $10^-3$
V =0.4 volt
Rm = 40 ohm
I = V/Rm = 0.4/40 = 0.01 Amp
m = I / Im = 0.01 / 4 x $10^-3$ = 2.5
Rs = Rm(m- 1)
Rs = 40*(2.5-1) =40*1.5 =60ohm
.
46. What will be the sensitivity (in Ohms/volts) of a PMMC type voltmeter when the
full-scale reading of the voltmeter is 240 V, the internal resistance of the voltmeter is 200
kilo-Ohms and the series resistance connected to the voltmeters is 80 kilo-Ohms?
V = 240 V Internal resistance of meter and series resistance total value = 200 kΩ + 80 kΩ = 280 kΩ sensitivity of voltmeter Sv = R / V = 280 $10^3$ /240 = 1166.67 Ω/V .
47. Determine the value of unknown inductance Lx, (in mH) and the effective
resistance Rx (in O) of inductor respectively for the circuit given below, if no current flows
through the galvanometer (G)?
In given circuit is maxwell capacitive inductance bridge-
R2 = 60 Ω
R3 = 40 Ω
R4 = 60 Ω
C4 = 40 μF
Rx = R2 * R3 / R4 = 60*40/60 = 40 Ω
Lx = R2*R3*C4 = 60*40*40$10^-6$ =96000 * $10^-6$
Lx = 96mH
.
48. What will be
the value of reactive power (in VAR) of a circuit having power factor of 0.5, when the apparent
power of the circuit is 80 VA?
Given
Apparent power 80VA
power factor cosθ =0.5
now Active power = Apparent power*power factor =80*.5 =40 watt
Reactive Power = √($Apparent power^2$ -$Active power^2$)
Reactive Power = √($80^2$ -$40^2$) = √(6400 - 1600)
Reactive Power = √4800 =69.6 watt
.
49. Determine the secondary voltage (in V) of a potential transformer when
the value of the system voltage is 11,000 V, the turn's ratio of the potential transformer is 102
and the percentage voltage error of the transformer is 3% ?
Nominal ratio= 102 error= 3% Primary voltage = 11000 Volt secondary voltage = S Volt Actual ratio of transformer =11000/N % error = (Nominal ratio - actual ratio)/actual ratio *100 0.03 = [102 -(11000/N)]/(11000/N) *100 N = 107.8 Volt .
50. Determine the quality factor for Maxwell's
inductance capacitance bridge given below when the bridge is supplied by a frequency of 50
Hz.?
Given
R2= 50Ω
R3= 30Ω
R4= 60Ω
C4= 20μF
f = 60Hz
Quality Factor (Q) = ω R4*C4
Quality Factor (Q) =2πf R4*C4
Quality Factor (Q) =2*3.14*50*60*20*$10^-6$
Quality Factor (Q) =0.4
.
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