Exercise: Exam Question Papers

Questions for: Exam Question Papers

With respect to the following 555 timer circuit what will be the value of RA and R such that the LED turns on for a duration of 10 ms every time it receives negative trigger pulse. LED operating current = 20 mA, Vf = 1.4 V, Vo on = 13.4 V and C = 0.22 nf
A:
41.4 KΩ, 600 Ω
B:
45 KΩ, 630 Ω
C:
43.5 KΩ, 580 Ω
D:
44.9 KΩ, 600 Ω
Answer: A

Timer operated in mono, mode

RAC =

∴ RA = 41.4 KΩ

R = = 600 Ω.

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The Laplace transform of the given waveform is
A:
(1 - e-s + e-2s)
B:
(1 - e-s + e-2s)
C:
(1 - 2e-s + e-2s)
D:
(1 - 2e-s)
Answer: C

f(t) = f1(t) + f2(t) + f3(t)

= 2tu(t) - 2 x 2(t - 1) + 2(t - 2)u(t - 2)

f(s) = - e-s + e-2s

= (1 - 2e-s + e-2s).

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The signal flow graph of a system is shown in figure. The transfer function of the system is :
A:
B:
C:
D:
Answer: D

P1 = 1 [Path R(s to C(s)]

Δ = 1 - (L1 - L2 + L3) + L1L2

P1 = 1; Δ1 = 1

[Non touching loop gain to forward path]

.

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A transmitted using AM has in modulated carrier output power of 10 KW and can be modulated to a maximum depth of 90% by a sinusoidal modulating voltage without causing overloading. Find the value to which an modulated carrier power can be increased without resulting in overloading if the maximum permitted modulating index is 40%
A:
14 KW
B:
12.96 KW
C:
26.96 KW
D:
2.96 KW
Answer: B

Now PT is fixed, μ = 0.4

Then PC is PC =

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A control system is as shown in given figure The maximum value of gain K for which the system is stable is
A:
more than 5
B:
equal to 5
C:
less than 1
D:
less than 5
Answer: D

Characteristic Equation is 1 + GH = 0

1 +

or s3 + 3s2 + 2s + (1 + K) = 0

Hurwitz criterion can be applied

s3 1 2 and (1 + K) both should be + ve

s2 3 1 + K

s1 0 ∴ K should be more than - 1 and less than 5

s0 1 + K.

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