Exercise: Exam Question Papers

Questions for: Exam Question Papers

In a series LCR circuit the maximum inductor voltage is twice the maximum capacitor voltage however current lags by 30° and drop across the inductance is vL = 100 sin 377t V. Assuming the resistance being 20 Ω, Find the values of the capacitance and inductance.
A:
235 μF, 61.18 μH
B:
230 μF, 61.18 μH
C:
61.18 μF, 230 μH
D:
None of the above
Answer: B

vL max = 100 V = ωL Imax

2Imax = ωL X ωC Imax

ω2LC = 2

ω2LC = 2

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Determine the voltage VCB in the circuit below:
A:
3.4 V
B:
5.4 V
C:
7.4 V
D:
9.4 V
Answer: C

= 2.3 mA ≈ IC

VCB = CCC - ICRC = 12 - 2.3 x 2 = 7.4 V.

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4 point DFT for x(n) = {2, - 1, 2, 3} is
A:
{6, 4 - 2j, 2, 2j}
B:
{6, 4j, 2, - 4j}
C:
{6, -1 + 3j, 4 - 4j, 4 - 2}
D:
{6, 2j, 4 - 2j, - 2 + 2j}
Answer: B

1 point DFT

X(k) = [W][x(n)]1

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VL = 100 cos (10t + 30°)
R = 10 Ω XL = j10 Ω
XC = - j4 Ω

Find Vs
A:
116.57 sin (10t - 29°) V
B:
116.57 sin (10t + 29°) V
C:
117.00 sin (10t - 29°) V
D:
117.00 sin (10t + 29°) V
Answer: A

VC = XC X I = 7.07 X 4∠ -90° - 60° = 28.28∠ - 150°V

VR = I X R = 7.07 ∠-60° x 10 = 70.7∠ - 60°

Vs = 70.7∠30° + 70.7∠-60° + 28.28∠-150° = 82.44∠-29° V

vs = 116.57 sin (10t - 29°) V.

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A n-type silicon sample contains a donor concentration of Nd = 2 x 1016 cm-3. The minority carrier hole lifetime is tp0 = 5 μs. The thermal equilibrium generation rate of hole is:
A:
1.125 x 109 cm-3 s-1
B:
0.625 x 109 cm-3 s-1
C:
4.5 x 109 cm-3 s-1
D:
2.25 x 109 cm-3 s-1
Answer: D

Then thermal generation rate

= 2.25 x 109 cm3 S-1 .

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