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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 11
1.
The circuit in figure, is to be scaled to an impedance level of 5kΩ and resonant frequency of 5 x 106 rad/sec. The possible combination of R, L, C is
2.5Ω, 0.2 mH, 200 pF
5 kΩ, 0.2 mH, 200 pF
5 kΩ, 0.2 mH, 200 μF
5 kΩ, 0.1 mH, 0.4 μF
Answer: Option
Explanation:

If L = 0.2 mH and C = 200 pF, ω0 = 5 x 106 rad/sec and if R is 5 kΩ, impedance level is 5 kΩ.

2.
In figure, the total power consumed is
10 W
12 W
16 W
20 W
Answer: Option
Explanation:

Use superposition theorem.

3.
If operator 'a' = 1 ∠120° then (1 + a) =
-a
-a2
a
-1
Answer: Option
Explanation:

Since 1 + a + a2 = 0, 1 + a = - a2.

4.
A current wave is i = 100e-60t The initial and final values of current are
100 and 50
100 and 0
0 and 100
100 and 100
Answer: Option
Explanation:

i(0) = 100 e-0 = 100, i(∞) = 100 e-∞ = 0.

5.

Assertion (A): The impedance of a series resonant circuit is minimum at resonance.

Reason (R): Resonance condition implies unity power factor condition.

Both A and R are true and R is correct explanation of A
Both A and R are true and R is not the correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

Since power factor is unity, impedance is minimum.

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