Electronics-sample-paper-5.pdf

Q.l- Q.25 carry one mark each. Q.1

Jexd~ 1 is equal to (A) log (ex - 1) (C) log ( e

Q.2

x -

(B) log ( 1 - ex)

1)

(D) log(l- e x)

I I<

Expand the function (z-1)\z- ) in laurent's series for z 1 2 1 3 7 2 15 3 7 2 15 2 (A) 1 +3z+ 2 z +-:rz ... (B) 2 +4z+8z + 16 z ... (D) None of the above

Q.3

If A is a square matrix of order 3 and 1 A 1 = 2 then A ( adj A) is equal to

+0

2 0 0 (A) 0 2 0 0 0 2 1

(B) 0 0

Q.S

Q.6

+

(D) None of these

Consider a ufb system with forward-path transfer function G(s) . system IS stable for the range of K;

(A) K > 0

(B) K < 0

(C) K > 1

(D) Always unstable

=

~~s+ 3;. s s+ 2

The

. . . The t Ime 1 correspond.mg t o 2i82 +lOs+ signa + + 11 IS 58 6

(A) 26(t) + (e 3t- e 2 t) u(t)

(B) 26(t) + (e 2t- e 3 t)u(t)

(C) 26(t) + (e 2t+ e 3 t) u(t)

(D) 26 (t) - ( e 2t + e 3 t) u ( t)

The characteristic equation of a closed-loop system is s(s+ 1) (s+ 2) + K = 0. The centroid of the asymptotes in toot-locus will be (B) - 1 (A) 3

(D) -3

(C) 1 Q.7

0

0 0

(C) 0 1 0 0 0 1 Q.4

t

0 0

Given the z- transforms X( z)

(A) 1 (C) oo

=

4

~(Sz- 7)

- 7z + 3

the limit of x[oo] is

(B) 2 (D) 0

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Q.8

For the block diagram shown below transfer function C(s) / R(s) is

14-------....-----C(s) R(s)

+

+

Q.9

For the signal x(t) =2(t-l)u(t-1)-2(t-2)u(t-2)+2(t-3)u(t-3) The correct waveform is

2

(A)

(B) --------1-_..__-----'---'-----

0

1

2

3

t

0 1 2 3 ------1---...--------.---.----- t

(C)

(D) -2

Q.10

Q.11

The function Z1 is

(A) a+ b + c

(B) ab + ac + be

(C) a 0 b 0 c

(D) a E8 b E8 c

If (211)x = (152) 8 , then the value of base xis

(A) 6

(B) 5

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(C) 7 Q.12

(D) 9

For the circuit shown below the input voltage v, is as shown in figure.

c 10

+ R

-10

Assume the RC large and cutin voltage of diode V, = 0. The output voltage

(A)

10

Q.14

is

l

(C)

Q.13

V0

(D)

An ideal pn junction diode is operating in the forward basic region. The change in diode voltage, that will cause a factor of 9 increase in current, is (A) 83 mV

(B) 59 mV

(C) 43 mV

(D) 31 mV

If the base width of a bi-polar transistor is increased by a factor of three then what is the collector current change ? (A) Increased by a factor of three

(B) Decreased by a factor of three

(C) Neither increased nor decreased (D) Collector current is independent of base width Q.15

For a n-channel enhancement-mode MOSFET the parameters are VTN = 0.8 V, 2 k ~ = 8 ~A/V and W/ L = 5. If the transistor is biased in saturation region with In= 0.5 rnA, then required VcB is (A) 1.68 V

(B) 2.38 V

(C) 4.56 V

(D) 3.14 V www.examrace.com

Q.16

The value of the current measured by the ammeter in figure is 2A

3A

(A)

iA

(B)

(D)~

(C) - 5 A 6 Q.17

iA A

In the given lattice network the value of RL for the maximum power transfer to it is 70

(A) 6.67 (C) 6.52 Q.18

n (D) 8 n

n n

(B) g

In the following circuit, the switch S is closed at t = 0. The rate of change of current

~~ (o+)

is given by S

R

L

Q.19

(A) 0

(B) RLis

(C) (R +LRs) Is

(D)

Let J = 25 u P - 2 20 u z A/m 2 . The value of P p + O.Olpx (A) 7.8 A/ m 2

co

aaPv is t

(B) -4.6 A/ m 2

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(C) 4.6 A/m 2 Q.20

(D) 0 2

(C) Plane x = 3~ Q.21

Q.22

Q.23

Q.24

Q.25

2

A vector field is E = 4zy ux + 2ysin 2xuy + y sin 2xuz The surfa ce on which Ey = 0 is (A) Plane y = 0 (B) Plane x = 0

(D) all

In a nonmagnetic medium, E=5cos(10 9 t-8x)ux+4sin(10 9 t-8x)u z V/m. The dielectric constant of the medi urn is

(A) 3.39

(B) 1.84

(C) 5.76

(D) 2.4

The aerial current of an AM transmitter is 18 A when unmodulated but increases to 20 A when modulated. The modulation index is (A) 0.68

(B) 0. 73

(C) 0.89

(D) None of the above

A carrier is phase modulated (PM) with frequency deviation of 10 kHz by a signal tone frequency of 1 kHz. If the signal tone frequency is increased to 2 kHz, assuming that phase deviation remains unchanged, the bandwidth of the PM signal is (A) 21 kHz

(B) 22 kHz

(C) 42kHz

(D) 44kHz

A die is thrown thrice. Getting 1 or 6 is taken as a success. The mean of the number of successes is

(A) 3/2

(B) 2/3

(C) 1

(D) None

Let f(x) = ex in [0, 1]. Then, the value of c of the mean-value theorem is (A)0.5 (C) log ( e- 1)

(B)(e-1) (D) None

Q.26- Q.55 carry two mark each. Q.26

For dyj dx = xy given that y = 1 at x = 0. Using Euler method taking the step size 0.1, the y at x = 0.4 is www.examrace.com

Q.27

Q.28

(A) 1.0611

(B) 2.4680

(C) 1.6321

(D) 2.4189

The solution of

~; -

ytan x- y 2 sec x = 0 is

(A) y 1 = sin x + c1 cos x

(B) y

1

=-

(C) y = cosx+ c3 sinx

(D) y

1

=- cos x + c4sinx

[

1

1 [

1 [

ex+y+z dxdydz is equal to

(A)(e-1) 3 (C) (e- 1) Q.29

2

(B) 3 (e- 1)

2

(D) None of these

A lossless transmission line with a characteristic impedance of 80 D is terminated by a load of 125 D. The length of line is 1.25-A. The input impedance is (B) 51.2 n (A) 80 n (C) 125

Q.30

sinx+ c2 cosx

n

(D) 45

n

In a nonmagnetic medium (cr = 6.25) the magnetic field of an EM wave 1s H = 6 cos ,Bxcos (10 8 t) u z A j m. The corresponding electric field is (A) 903sin (0.83 x)sin(10 8 t)uy V/m (B) 903sin(1.2x)sin (10 8 t)uy V/ m (C) 903sin (0.83 x)cos (10 8 t) u y V/ m (D) 903sin (l.2x)cos (10 8 t) u y V/m

Q.31

The plane 2x + 3y- 4z = 1 separates two regions. Let f.1r1 = 2 in region 1 defined by 2x+ 3y- 4z > 1, while /11'2 = 5 in region 2 where 2x + 3y- 4z < 1. In region H 1 = 50ux- 30u y + 20uz Ajm. In region 2,H 2 will be (A) 63.4u x + 43.18uy + 19.4uz A/ m (B) 52.9ux - 25.66u y + 14.2uz A/ m (C) 48.6ux - 16.4uy- 46.3u z A/ m

(D) None of the above

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Q.32

Q.33

A total of 30 equal-power users are to share a common communication channel by CDM. Each user transmit information at a rate of 10 kbps via DS spread spectrum and binary PSK. The minimum chip rate to obtain a bit error probability of 10 5 (A) 1.3

X

10 6 chips/sec

(B) 2.9

X

10 5 chips/sec

(C) 1.9

X

10 6 chips/sec

(D) 1.3

X

10 5 chips/sec

The channel capacity of the binary symmetric channel shown below is P(xt) =a

xt 0:::------=------:::0 Y1

22 CF----------:::--------'0 Y2

P(22)

Q.34

Q.35

Q.36

= 1-a

(A) qlog2q+ plog2p

(B) 1- plog2p- qlog2q

(C) - qlog2q+ plog2p

(D) 1 + qlog2q+ plog2p

It was found that a sampling rate 20% above the rate Would be adequate. So the maximum SNR, that can be realized without increasing the transmission bandwidth, would be

(A) 64.4 dB

(B) 70.3 dB

(C) 50.1 dB

(D) None of the above

A superheterodyne FM receiver operates in the frequency range of 88-108 MHz. The IF and local oscillator frequency are chosen such that ftF < fw. The infe frequency must fall outside of the 88-108 MHz region. The range of variation in fw is (A) [98, 128] MHz

(B) [78, 128] MHz

(C) [98, 118] MHz

(D) [78, 98] MHz

A state-space representation of a system is given by

x~[-~ ~]x, y~ [1

-l]x, and x(O)

~[~]

The time response of this system will be (A) sin/2 t (C) -

}s sin/2 t

(B) --}:;sin/2 t (D)

.f3 sin/2 t

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Q.37

Consider a ufb system whose open-loop transfer function G(s) = Nyquist plot for this system is lm

I

/

K

) . The

+ 2s + 2

'\

w= oo \

(A)

2

Im

-.......,

r

( 8 8

' / _....,,

I

I

Re

(B)

lm

Re

w=oo

lm

(C)

Q.38

Consider the system shown below. R(s)

+-0 -

K

s( s+l )( s+4)

C(s)

: (s+a): The sensitivity of the steady state error to parameter a to step input is

(B) ex c2 1

(A) ex~ 1 2

(D) _ex_ ex-1

(C) _ex_ ex -1 Q.39

Suppose we have given following information about a signal x(t) : 1.

x( t) is real and odd.

2.

x( t) is periodic with T = 2

3.

Fourier coefficients X[k] = 0 for [ k [ > 1

4.

i[

2 [

x(t) [2 dt

= 1

The signal, that satisfy these condition, is www.examrace.com

(A)

12sin 11:t

and unique

(C) 2 sin 11:t and unique Q.40

Q.41

12 sin 11: t

but not unique

(D) 2sin11:t but not unique

If the input to this system is x( t) = cos (211:t +B), then output will be

3~ sin (211:t +B)

(A) -jsin (211:t +B)

(B)

(C) 2; sin(211:t+ B)

(D) None of the above

Two causal finite length sequences are given following. {y[n]} = {6,11, -13,16,1,9,2,8} and {h[n]} = {2,5, -1,4} If y[n] = h[n] * x[n], then sequence x[n] is (A){- 2,0,1,2} (B) {3,- 2,0,1,2} (C) {6,2, 5,- 1,4}

Q.42

(B)

(D) {6,11,-13,16,1}

Consider the following 8085 assembly program MVI A, DATAl MOVB, A SUI 51H JC DLT MOV A, B SUI 82H JC DSPLY DLT: XRA A OUT PORTl HLT DSPLY: MOV A, B OUT PORT2 HLT This program will display (A) the bytes from 51H to 82H at PORT2 (B) OOH AT PORTl (C) all byte at PORTl (D) the bytes from 52H to 81H at PORT 2

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Q.43

The frequency of oscillation of the astable multivibrator shown below is 6.8 kO

24 kO

-12

v

o.o33 ~FJ

..

Q.44

(A) 18.4 kHz

(B) 9.86 kHz

(C) 98.6 kHz

(D) 1.84 kHz

The counter shown in figure below is a

c.___r:-

-

J

Q

~

-

c -

'-----

Q

I

Q.45

J r- 1

Q A

B K -

Q

J

Q

K r- 1

Q

K

1

1

CLK

(A) MOD-8 up counter

(B) MOD-8 down counter

(C) MOD-6 up counter

(D) MOD-6 down counter

The circuit shown below has 4 boxes each described by input P, Q, R and output Y, Z with Y = P EB Q EB R and Z = PQ + P R + QR. Q

,........_.....

Output

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The circuit act as a 4 bit

Q.46

(A) adder giving P+ Q

(B) subtract or giving P

(C) subtractor giving Q ~ P

(D) adder giving P

Q

+ Q+ R

Consider the ideal op-amp circuit shown below

If it is given that (A) 20.8 dB

~~ =

10,

~: =

11. The common mode rejection ratio (CMRR) is

(B) 47.6 dB (D) 23.8 dB

(C) 41.6 dB Q.47

~

In the circuit shown below the Q-point is in the center of the load line. The transistor parameters are ~ = 150 and VA = co . +5V

··f

o.2 kn -5V

The small-signal voltage gain A v =

Vo

v.

is

(A)

~ 16.43

(B)

~9.438

(C)

~5.75

(D)

~3 .94

Common Data for Q. 48-49 : Q.48

A 2.4 em X 1.5 em wave guide operates in TE10 mode a t 9 GHz. The guide is made of brass (ac = 1.1 X 107 S/m) and filled with teflon (cr = 2.6,aa = 10 15 S/m). The attenuation constant, due to conduction losses, ac is www.examrace.com

Q.49

(A) 0.0395

(B) 0.022

(C) 0.0145

(D) 0.0193

The attenuation constant due to dielectric losses is 10

12

Np/m

(B) 1.3 X 10

(C) 2.4 x 10

11

Np/m

(D) None of the above

(A) 5.9

X

13

Np/m

Common Data for Q 50-51 : Consider the system shown below .The average value of m( t) is zero and maximum value of [ m(t) isM. The square-law device is defined by y(t) = 4x(t) + 10x(t). J

~

m(t)

Q.50

Q.51

x( t)

Ll

Square-Law Device

Y( t)

1---- AM Signal

.....__ _.

The value of M, required to produce modulation index of 0.8, is

(A) 0.32

(B) 0.26

(C) 0.52

(D) 0.16

Let W be the bandwidth of message signal m(t). AM signal would be recovered if

(A) ]c > W

(B) ]c > 2 W

(C) !c> 3W

(D) fc > 4 W

Statement for Linked Answer Q. 52-53: Q.52

In n-type silicon MOS structure a metal-semiconductor work function difference of ms =- 0.35 V is required. If gate is n+ polysilicon the required silicon doping required is

10 11 em

3

(B) 4 X 10 13 em

(C) 4 X 10 16 em

3

(D) Cannot use n+ polysilicon gate

(A) 4

Q.53

X

3

If gate is p+ polysilicon, then the required silicon doping is (A) 8 X 10 11 cm

3

(B) 8 X 1013 cm

3

(D) Cannot use n+ polysilicon gate www.examrace.com