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Electronics and Communication Engineering - Exam Questions Papers

Exercise : Exam Questions Papers - Exam Paper 2
46.
For a second-order system with the closed-loop transfer function The settling time for 2-percent band, in seconds, is :
1.5
2.0
3.0
4.0
Answer: Option
Explanation:

.

47.
An open loop transfer function is given by has
one zero at ∞
two zeros at ∞
three zeros at ∞
four zeros at ∞
Answer: Option
Explanation:

The root locus is given below.

From root locus, we can see that there are 3 zeros at ∞ .

48.
The current i(t) through a 10 Ω resistor in series with an inductance is given by i(t) = 3 + 4 sin (100t + 45°) + 4 sin (300t + 60°) Amperes. The RMS value of the current and the power dissipated in the circuit are
41 A, 410 W respectively
35 A, 350 W respectively
5 A, 250 W respectively
11 A, 1210 W respectively
Answer: Option
Explanation:

Power = I2R = 25 X 10 = 250 Watts.

49.
The cut off voltage for JFET is 5 V. The pinch off voltage is __________ .
(5.0)l/2 V
2.5 V
V
5 V
Answer: Option
Explanation:

For JFET

ID = IDSS (1 - VGS/Vp)2

0 = (1 - VGS/Vp)2

∴ VGS = VP

∴ Vp = 5 V.

50.

Assertion (A): Conductors do not permit propagation of waves more than a short distance into the conductor at microwave frequencies.

Reason (R): The relaxation time constant for conductors is much small than the period of centimetric EM wave.

Both (A) and (R) are true and (R) is the correct explanation of (A)
Both (A) and (R) are true but (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:

Depth of penetration = , where = relaxation time.

δ would be small, if σ is large, which itself depends upon relaxation time.

t for conductors is of the order of 10-14 s, for λ = 3 x 10-2 cm

∴ period of centimetric EM waves

=

Therefore, even though t is much smaller than period of centimetric waves but it is not the correct reason for the assertion given.

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