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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 13
31.
In a series RLC circuit the dB level of currents at half power frequencies as compared to current at resonance is
+ 3
- 3
0.5
- 0.5
Answer: Option
Explanation:

At half power frequencies, current is - 3 dB.

32.
A series RL circuit is initially relaxed. A step voltage is applied to the circuit. If t is the time constant of the circuit, the voltage across R and L will be same at time t equal to
t ln 2
Answer: Option
Explanation:

i = i0 (1 - e-R/Lt) and VR = VL at a given time t.

33.
In figure, the transmission parameters are A = C = 1, B = 2 and D = 3. Then Zin =
12/13 Ω
13/12 Ω
3 Ω
4 Ω
Answer: Option
Explanation:

34.
A sinusoidal voltage is written as v = Im (R2 + XC2)0.5 sin 314 t. Its peak value and frequency are
Im and 50
Im (R2 + X2C)0.5 and 50
0.707 Im (R2 + X2C)0.5 and 50
2 Im (R2 + X2C)0.5 and 50
Answer: Option
Explanation:

v2 = sin (ωt + 90°)

35.
If A = 10 + j then logeA is
14.14 ∠45°
200 ∠45°
2.65 + j45°
2.65 + j0.785
Answer: Option
Explanation:

A = 14.14Ð45°, loge A = loge 14.14 x = 2.65 + j 0.785.

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