All India Institute of Medical Sciences 2007 B.Com Computer Science Auto cad University - Question Paper

An electromagnetic wave with electric field E1 = 4a + 3a + 5a is incident normally on the
interface form region-I. The electric field E2 in region-Il at the interface is:
Region I Region II
= °P1 = = °P2 =
E1 E
xO
(A) E2=E1
(B) 4a +0.75a —1.25a
(C) 3a+3a+5a
(D) —3a + 3a + 5a
54. A rectangular waveguide having TE10 mode as dominant mode is having a cutoff
frequency of 18-GHz for the TE30 mode. The inner broad-wall dimension of the rectangular
waveguide is:
(A) 5— cms
(B) five cms
(C) eight cms
(D) 10 cms
55. A mast antenna consisting of a 50 meter long vertical conductor operates over a perfectly
conducting ground plane. It is base-fed at a frequency of 600 kHz. The radiation resistance of
the antenna in Ohms is:
(A)
(B)
(C)
(D) 20,r2
Common Data Questions:
Common Data for ques. 71, 72, 73:
In the transistor amplifier circuit shown in the subsequent parameters:
I3DC = 60, “BE = 0. 7V, hie — 00, hfe °° The capacitance Ccan be presumed to be infinite.
5.3K
figure below, the transistor has the
1 2V
In the figure above, the ground has been shown by the symbol V
71. Under the DC conditions, the collector-to-emitter voltage drop is:
(A) 4.8 Volts
(B) 5.3 Volts
(C) 6.0 Volts
(D) 6.6 Volts
72. If I3DC is increased by 10°h, the collector-to-emitter voltage drop
(A) increases by less than or equal to 10%
(B) reduces by less than or equal to 10%
(C) increases by more than 10%
(D) reduces by more than 10°h
73. The small-signal gain of the amplifier v/v is:
(A) -10
(B) -5.3
(C) 5.3
(D) 10
Common Data for ques. 74, 75:
Let g(t) = p(t) * p(t), where * denotes convolution and p(t) = u(t)— u(t —1) with u (t) being
the unit step function
74. The impulse response of filter matched to the signal s (t) = g (t) — —2) * g (t) is
provided as:
(A) s(1—t)
(B) —s (1 — t) T EForum
(C) —s(t)
(D) s(t)
75. An Amplitude Modulated signal is provided as
XAM (t) = 100(p(t)+0.5g(t))cosat
in the interval 0 < t < 1. 1 set of possible values of the modulating signal and modulation
index would be
(A) t,O.5
(B) t,1.O
(C) t,2.O
(D) t2,0.5
Linked ans Questions: Q.76 to Q.85 Carry 2 Marks every.
Statement for Linked ans ques. 76 & 77:
A regulated power supply, shown in figure below, has an unregulated input (UR) of 15 Volts
and generates a regulated output Use the component values shown in the
figure.
In the figure above, the ground has been shown by the symbol V
76. The power dissipation across the transistor Qi shown in the figure is:
(A) 4.8 Watts
(B) 5.0 Watts
(C) 5.4 Watts
(D) 6.0 Watts
77. If the unregulated voltage increases by 20%, the power dissipation across the
transistor Qi
(A) increases by 20°h
(B) increases by 50°h
(C) remains unchanged
(D) reduces by 20°h
Statement for Linked ans ques. 78 & 79:
The subsequent 2 ques. refer to wide sense stationary stochastic processes
78. It is desired to generate a stochastic process (as voltage process) with power spectral
density By driving a Linear-Time-Invariant system by zero mean white noise (as voltage
process) with power spectral density being constant equal to 1. The system which can perform
the desired task could be:
(A) 1st order lowpass R-L filter
(B)
(C)
(D)
Statement for Linked ans ques. 80 & 81:
Consider the subsequent Amplitude Modulated (AM) signal, where m
XAM (t) = 10(1 + 0.5sin2rfmt)cos2rft
avg. side band power fo tie AM signal provided above is:
81. The AM signal gets added to a noise with Power Spectral Density S (f)given in the figure
below. The ratio of avg. sideband power to mean noise power would be:
(A) 25
(B) 12.5
(C) 6.25
(D) 3.125
Statement for Linked ans ques. 82 & 83:
Consider a unity-gain feedback control system whose open-loop transfer function is:
first order highpass R-c filter tuned L-C filter
series R-L-C filter
82. The value of “a” so that the system has a phase margin equal to -is
approximately equal to
(A) 2.40
(B) 1.40
(C) 0.84
(D) 0.74
83. With the value of “a” set for a phase-margin of the value of unit-impulse
response of the open-loop system at t = one 2nd is equal to
(A) 3.40
(B) 2.40
(C) 1.84
(D) 1.74
Statement for Linked ans ques. 84 & 85:
A 30-Volts battery with zero source resistance is connected to a coaxial line of characteristic
impedance of 50 Ohms at t = 0 2nd terminated in an unknown resistive load. The line
length is that it takes 400 ps for an electromagnetic wave to travel from source end to load
end and vice-versa. At t = 400ps, the voltage at the load end is obtained to be 40 Volts.
84. The load resistance is
(A) 25 Ohms
(B) 50 Ohms
(C) 75 Ohms
(D) 100 Ohms
85. The steady-state current through the load resistance is:
(A) 1.2 Amps
(B) 0.3 Amps
(C) 0.6 Amps
(D) 0.4 Amps

Earning:   Approval pending.