UPSC_Exams > UPSC_Indian_Engineering_Services_Answer > UPSC_IES_EC_2014_Answer_Key_Question_par
ENGINEERING > ELECTRONICS
1) In a JFET operating above pinch-off voltage, the
A) drain current increases steeplyB) drain current remains practically constant
C) drain current starts decreasingD) depletion region reduces
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Answer : drain current remains practically constant


ENGINEERING > ELECTRONICS
2) If VCC = 18V, voltage. divider resistances
R1 =4.7k? and R2 = 1500 ?, what is the base bias voltage
A) 8.70 VB) 4.35 V
C) 2.90 VD) 0.70 V
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Answer : 4.35 V


ENGINEERING > ELECTRONICS
3) An SCR has an anode supply of sine voltage 200Vr.m.s, 50 Hz applied through a 100 ? resistor and fired at an angle of 60. Assuming no voltage drop, the r.m.s. value of the output voltage is nearly
A) 90 VB) 126 V
C) 166 VD) 200 V
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Answer : 126 V


ENGINEERING > ELECTRONICS
4) In a GTO, anode current begins to fall when gate current
A) is negative peak at time t = 0B) is negative peak at time t = storage period
C) just begins to become negative at t = 0D) just begins to become positive at t = 0
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Answer : is negative peak at time t = storage period


ENGINEERING > ELECTRONICS
5) An SCR is turned off when its turn-off time is
A) less than the circuit time constantB) greater than the circuit time constant
C) less than the circuit turn-off timeD) greater than the circuit turn-off time
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Answer : less than the circuit turn-off time


ENGINEERING > ELECTRONICS
6) A system is characterized by the input-output relation
y(t) = x(2t) + x(3t)
for all t, where y(t) is the output and x(t) is the input. It is
A) linear and causalB) linear and non-causal
C) non-linear and causalD) non-linear and non-causal
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Answer : linear and non-causal


ENGINEERING > ELECTRONICS
7) A discrete-time system has input x[.] and output y[.] satisfying
y[m]= ?mj=-? the system is
A) linear and unstableB) linear and stable
C) non-linear and stableD) non-linear and unstable
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Answer : linear and unstable


ENGINEERING > ELECTRONICS
8) The Fourier transform of a rectangular pulse for a period
t = - T2 to T2 is
A) a sinc functionB) a sine function
C) a cosine functionD) a sine-squared function
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Answer : a sinc function


ENGINEERING > ELECTRONICS
9) The current waveform i(t) in a pure resistor of 20 ? is shown in the figure.
The power dissipated in the resistor is
A) 135 W
B) 270 W
C) 540 W
D) 14.58 W
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Answer : 540 W


ENGINEERING > ELECTRONICS
10) A p-type silicon sample has ah intrinsic carrier concentration- of l-5xl0l0/cm3 and a hole concentration of 2-25xl015/cm3. Then the electron concentration is
A) l.5x1025/cm3B) 105/cm3
C) 1010/cm3D) 0
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Answer : 105/cm3