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Institute Of Engineering Studies Mock Test- I

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ELECTRONICS & COMMUNICATION Max Marks = 100

Q.Nos 1 to 25 will carry one mark each Total Duration = 3 hours 1.What is the time function vx(t) for the circuit shown in figure if ω = 100 rad/s

↑ j 60_

+_

50

+0.4 VV

j 12

x x_

_j 25

= As

I

a. vx(t) = 100 cos(100t – 36.87

0) V b. vx(t) = 250 cos(100t – 36.87

0) V c. vx(t) = 100 sin(100t – 36.87

0) V

d. vx(t) = 150 sin(100t – 36.870) V

2.Consider the circuit of figure , suppose vs(t) = 30 u(t) V, Zs = 1Ω, ZL = 20 Ω, and the z-parameter matrix is

Then Zin and Zout are

V

Z

V

_

I1

Z

+

V_

I

Z→

Z

in

Two-Port_

+

→

↑

o

oo

o

2s

+

L

↑s

out

2

1

a.4 Ω, 34 Ω b. 5 Ω, 30 Ω c. 5.75 Ω, 34 Ω d. 5.75 Ω, 24 Ω 3.Consider the graph and tree of a network , shown in the figure , the number of twigs and links of the network are respectively,

4

2 3

5

6

1

2 3

6

a. 1,3 b. 5,1 c. 2,1 d. 4,2

Q4. Match List-I with List-II select the correct answer using the codes given below the lists: List-I List-II a. Drift current charge 1. Law of conservation b. Einstein’s equation 2. Electric field c. Diffusion current 3. Thermal voltage d. Continuity equation 4. Concentration gradient Codes: A B C D a. 2 1 4 3



b. 4 3 2 1 c. 4 1 2 3 d. 2 3 4 1 Q5. A particular Red LED emits light of wavelength 7600 A

0. The energy band gap of the semiconductor material

used there is (Planck’s constant = 6.626 x 10-34

J-S) a. 2.26 e V b. 1.17 eV c. 1.63 eV d. 0.74 e V

Q6. In the case of the circuit shown in the figure the collector current Ic will be

3k20 k

+ 12 V

2 k

→

12 k

= 100

VBE

A

= 0.7 V

Ico= 0.01 20

oCat

a. 2.26 mA b. 1.85 mA c. 0.375 mA d. 0.185 mA

Q7. A resistance thermometer has a temperature coefficient of resistance 10-3

per degree and its resistance at 00 C is 1.0 Ω. At what

temperature is its resistance 1.1 Ω? a. 10

0 C b. 100

0 C

c. 1200 C d. – 10

0 C

Q8. The logic realized by the circuit shown in figure is

I

I

I

I

2

3

F

S S01

4 to1 MUX

0

1

_

C

C

A B

a. b.

c. d.

Q9. In a J-K flip-flip we have J = and K=1. (See Fig.) Assuming the flip flop was initially cleared and then clocked for 6 pulses, the sequence at the Q output will be

QJ

_

K

Q

QCK1



a. 010000 b. 011001 c. 010010 d. 010101 10.For the circuit shown, VCE and VBE are related by , (assume β to be very high )

6 V

CE

2k

2k

2k

2k

V

a. VCE = VBE b. VCE = 2 VBE c. VCE = ½ VBE d. VCE = 0 11.For the op-amp, BJT circuit shown assume β =4 for BJT , and op-amp to be ideal. Which is the correct statement ,assume BJT be in active region and power supply will be ± 10 V

A

3 K

BVo

6 V

3 V

1 K

a. terminal A is inverting and V0 = 1V b. terminal A is non-inverting and V0 = 1V c. terminal A is inverting and V0 = 1.25V d. terminal A is non-inverting and V0 = 1.25V 12.If mid-band gains from Vi to V0 under the condition when switch S is open and closed are A1 and A2 respectively , then A1/ A2 is given by, neglect hie of the BJT

DD

BB

R

V

R

i

E

V

B

C

o

~ S

R

CV

V



a. b. c. d. 1 13.The input x and output y of a system are described by the differential equation :

Determine how the output will vary with time when there is an input which starts at zero time and then increases at the constant rate of 6 units/s. The initial output is zero a.y(t) = 3t – 1.5 e

-2t – 1.5 b. y(t) =1.5t – 1.5 e

-3t – 1.5 c. y(t) = 3t – 3e

-2t – 3

d. y(t) = 3t – 1.5 e-1.5t

– 1.5 14.A system has a forward path transfer function of 10 / (s+3) and a negative feedback loop with transfer function 5. What is the time constant of the resulting first-order system ? a. 53 units b. 1.9 units c. 0.019 units d. 5 units 15.Consider the feedback control system

→Y(s)R(s) +

_ → →

↑

a.ωr = 3.26 rad/sec, ωb = 16.64 rad/sec b. ωr = 5.49 rad/sec, ωb = 11.6 rad/sec c. ωr = 1.59 rad/sec, ωb = 1.86 rad/sec d. ωr = 12.52 rad/sec, ωb = 3.25 rad/sec

16. The LTI system with impulse response a. stable and causal. b. stable and non causal c. unstable and non causal d. unstable and causal 17. 13. A discrete time system with transfer function H(z), has a real pole at z = a and a real zero at z= 1/a. The magnitude of frequency response |H(e

jω)| is

a. |H (ejω

)| = 1 b. c. d. |H (e

jω)| = a

18.A DSBSC signal is detected , by reinserting sufficient amount of carrier as shown in the figure below

envelope→ detector→ →

↑

y(t)

C(t)

+

The o/p y(t) after dc blocking is a.m(t) cos(δ) b. A cos(2π Δft +δ) + m(t) c. m(t) cos (2π Δft) d. m(t) cos (2π Δft +δ) 19. Let x(t) be a wide sense stationery random process with Rx x (τ) = 2 e

- |τ| -∞ < τ < ∞

The value of E [(x(t+1) – x (t-1))2] is

a.4 – e- 2

b. 2 – 2 e-2

c. 2 - 4 e- 2

d. 4 – 2 e -2

20. A line has Z0 = 70 Ω and phase constant of 3 rad/m, at 100 MHz. Calculate the inductance /m and capacitance /m of the line a.68.2 PF/m, 300 nH/m b. 300 PF/m,68.2 nH/m c. 68.2 PF/m, 334.2 nH/m d. 68.2 nH/m, 334.2 PF/m



21.If radiation resistance of an antenna Rrad = 2 Ω, and the power radiated Prad = 10 w, and Rrad to 10 Ω, what is power radiated now ? a.100 w b. 20 w c. 50 w d. 150 w

22.If A and B are mutually exclusive events, then

(a) P(AB) = P(A). P(B) (b) P(AB) = P(A) . P(B)

(c) P(AB) = O (d) P(AB) = O 23. The variance of the two-point distribution

Where p+q = 1 is

(a) ap + bq (b) bqap (c) pq(a-b)2 (d) 2pq

24. If ‘n’is the number of sub-intervals then which of the following is not a value for ‘n’ to use Simpson’s 3/8 rule. (a) 6 (b) 9 (c) 12 (d) 16 25. Consider the system of linear equations 3x-y=5,x+2y=4 using jacobi’s method at the end of sixth iteration value

of x & y will be(Starting value x=y=0)

(a) x=7/3,y=7/3 (b) x=3/5,y=4/5 (c) x=215/108 ,y=37/36 (d) x=315/53,y=314/27

Q.Nos 26 to 55 will carry two marks each 26.Find the Norton Equivalent for the circuit shown in figure

↓1

o

↓

0.06 V

30 mA100

400

1V+

_

o

a. 100 mA downward, -50 Ω b. 150 mA downward, -50 Ω c. 100 mA downward, -100 Ω d. 150 mA downward, -100 Ω 27. In the circuit shown in figure , the switch is closed at t =0 when the 6 µF capacitor has charge Q0 = 300 µC, then the expression for the transient voltage VR is

o

i

F

+

+

_

_

Q

20

1

26

VR

F

F

a. VR = 50 e

-t/40 b. VR = 25 e

-t/40 c. VR = 100 e

-t/40 d. VR = 10 e

-t/40

28. Consider the circuit in figure , in which Vin = 60 V, G1 = 0.1 S , G2 = 0.1 S, G3 = 0.3 S, G4 = 0.4 S, G5 = 0.1 S, G6 = 0.1 S, and G7 = 7/480 S, Find the equivalent resistance Req = Vin / Iin

X A b

f(x) P q



A

x

eq Reference node

x

C

v3

out

out7

V

→

↑

↓

|

_

↓6

+

+

+

_

G

in

v

R

G

I2

I

B

2G

G

G

G

G

1

3

4 5

I

in

+_

a. 6Ω b. 10 Ω c. 12 Ω d. 15 Ω 29. The current I in a forward biased P-N junction shown in figure (1) is entirely due to diffusion of holes from x=0 to x = L, The injected hole concentration distribution in the n-region is linear as shown in figure (2) with P (0) = 10

12/cm

3 and L= 10

-3 cm.

I

p n

0X

↑

0 LL→

p(X)

Hole

p(0)

Xdensity

Determine:

A.The current density in the diode assuming that the diffusion coefficient of holes is 12 cm2/sec.

a. 19.2 m A/cm2 b. 21.8mA/cm

2

c. 1.92 mA/cm2

d. 2.18 mA/cm2

B. The velocity of holes in the n-region at x=0 a. 12 x 10

2 cm/sec b. 12 x 10

3 cm/sec

c. 9 x 10 2 cm/sec d. 9 x 10

3 cm/sec

30. If the transistors in figure have high values of β and a VBE of 0.65 volt, the current I, flowing through the 2 kilo ohms resistance will be



1.65 k

1.85 k

+

I

1 k

2 k

10 V

6.5 k ↓

_

a. 1 mA b. 3.33 mA c. 0 d. 5 mA

31. The Karnaugh map of 4 variable Boolean functions A, B C, D is shown in figure X indicates ‘don’t care’ combinations. The minimal SOP expression for the function is

01 11

x

x

0

1 1 1

0 1

10

10AB

CD

00

01

11

0

00

10

1

1

1 1 1

a. b.

c. d. 32. Fig shows a mod-K counter, Here K is equal to

K K

Q QJ J

Q Q_ _

1

CLK

1

a. 1 b. 2 c. 3 d. 4



33. A 10-bit ADC with full-scale output voltage of 10.24 V is designed to have a ± LSB/2 accuracy. If the ADC is calibrated at 25

0 C and the operating temperature ranges from 0

0 C to 50

0 C, then the maximum net temperature

coefficient of ADC should not exceed a. ± 200 μ V/

0 C b. ± 400 μ V/

0 C

c. ± 600 μ V/0 C d. ± 800 μ V/

0 C

34. Match List-I (computer terms) with List-II (definitions) and select the correct answer using the codes given below the lists: List-I List-II a. TTL 1. Non-saturation type and high power consumption b. ECL 2. Low power consumption and high packing density c. CMOS 3. High switching speed and good fan-out capability d. I

2 L 4. Bipolar logic with high packing density

Codes: A B C D a. 3 1 2 4 b. 2 3 1 4 c. 4 3 1 2 d. 4 3 2 1 35.In the figure shown, what is the value of V0

+

2 K

10 V

3.6 K

3 K

100

1.2 K

Vo

_

a.10 V b. 8 V c. 6 V d. 2 V 36.As shown in the figure M1 and M2 are of same size M3 is triple in width as compared to M2 or M1. assume process parameter (Kn

’ ) is equal for all the devices. What is the value of V0 (Gate voltage of M2

is 1 V)

3 V

2 K

W/L ↑↑

3 V

500

Vo

1 V

M M3

3W/L

1

2

MW/L

→



a. 2 V b. 2.25 V c. 1 V d. can not be determined as gate voltage of M1 is not given 37.For the circuit shown assume op-amp to be ideal M1 and M2 are identical and have Kn

’ = 200 µA/v

2, w=

20 µm, L = 10 µm, VT = 1V. What is the value of V0

→

2 K

_→

5 V5 V

1 K

3 V

Vo

M M1 2

+

a.4.2 V b.3 v c. 4 V d. can not be determined as op-amp is in positive feedback 38.Input the op-amp circuit is sine wave of peak value of 10V. What is the duty cycle of output

a.0.55 b. 0.45 c. 0.5 d.1

39.A first order system when subject to a step input rises to 90 % of its steady state value in 20 s. Determine its time constant and the rise time assuming the rise time represents a 10% to 90 % rise to the steady-state value a.5.6 s, 20 s b. 0.5 s, 10s c. 8.7 s, 19s d. 12 s, 18.85 s 40.Consider a control system with unity feedback

→Y(s)R(s) +

_ → G(s)→

↑

Where

The gain and phase margin are a.closed-loop system is unstable b. GM = 20.4 dB, PM = 58.1

0 c. GM = 6.6 dB, PM = 60.4

0

d. GM = ∞ dB, PM = 58.10

41. The fourier transform of the o/p of the scheme shown below after using the first three terms in the power series of e

x is



ee →(.)

↓→→→

→

H( .f)

↑m(t)X

M

c(t)C(t) y( .t)

Where the carrier C(t) = cos 2π(590000) t and m(t) is base band signal with maximum frequency fm = 4 kHz, where fo = 590 kHz and B is 8 KHz. The formula for y(t) will be a.0.5 M(f – 1180 kHz) + 0.5 M(f+ 1180 kHz) b. 0.25 M(f – 590 kHz) + 0.25 M(f+590 kHz) c. 0.5 M(f – 560 kHz) + 0.5 M(f+ 560 kHz) d. 0.5 M(f – 590 kHz) + 0.5 M(f+ 590 kHz)+δ(f+590 kHz) 42.In the compact disc (CD) digital audio system, an analog signal digitized so that the ratio of peak signal power to the peak quantization noise power is at least 91 dB, the sampling rate is 44.1 kHz, what is the data rate in bits per second a.661500 b. 617400 c. 705600 d.44100

43.Let be Fourier series representation of two periodic signals with period T. The value of the integral

is

a. 0 b. 1 c. k+1 d.

44. Let the impulse response of an LTI system be which of the following is true? a. The system is stable and its step response is – In (t) b. The system is unstable c. The system is stable and its step response is not bounded d. The system is stable and its step response is given by In (t) 45.Using the bisection method find the negative root of x

3-4x+9=0 correct to the three decimal places

(a)-2.506 (b) -2.706 (c) -2406 (d) None

46.Use Secant method to determine the root of the equation xxex cos with initial

approximation x0 = 0 and x1 = 1. What is x2? (a) 1 (b) -2.178 (c) 0.3147 (d) 0.4467 47.The contents of Register (B) and Accumulator (A) of 8085 microprocessor are 49H and 3AH respectively . The contents of A and the status of carry flag (CY ) and sign flag (S) after executing SUB B instructions are a. A = F1 , CY = 1, S =1 b. A = 0F , CY = 1, S =1 c. A = F0 , CY = 0, S =0 d. A =1F , CY = 1, S =1 Common data Questions (48,49) For Problems 48 and 49, consider the block diagram of a mechanical system

↑→→ → Y(s)

-G(s)R(s)

+c →G (s)

With the open-loop transfer function



And a proportional- derivative (PD) controller

Gc (s) = K (1+Tds).

48.When Td =0, the PD controller reduces to a proportional controller , Gc(s) = K. In this case , use the Nyquist plot to determine the limiting value of K for closed-loop stability a. K = 2.4 b. 4.3 c. 0.5 d. 1.6 49.Using the value of K in above problem , compute the gain and phase margins when Td = 0.2 a. GM = 14 dB, PM = 27

0 b. GM = 20 dB, PM = 64.9

0 c. GM = ∞ dB, PM = 60

0 d. Closed-loop

system is unstable Common data Questions (50,51) 50.A conducting bar can slide freely over two conducting rails as shown in figure . Calculate the voltage induced in the bar

x

P

Q

(0,0)

→6 cm

Y

U

If the bar is staitioned at y= 8 cm, B = 4 cos 10

6t a2 mwb/m

2

a.19.2 sin 106t V b. 25 sin 10

3t c.29 sin 10

4 t d. 19.2 sin 10

7 t

51. The bar slides at a velocity of U = 20 ay m/s, B = 4 az m wb/ m2

a.- 5 mV b. – 12 mv c. – 4.8 mv d. 6 mv Linked questions(52,53) 52.A transistor class-C amplifier has a maximum permissible collector dissipation of 20 w and a collector efficiency of 75 % it is to be collector modulated to depth of 90 %, the maximum un modulated carrier power will be a.39.7 w b. 42.7 w c. 44.5 w d. none 53. The side band power generated will be a.11.3 w b. 12.5 w c. 17.3 w d. 15.9 w

Statement for Linked Answer Questions 54 and 55 Three values of x and y are to be fitted in a straight line in the form y=a+bx by the method of least squares. Given: ∑x=6, ∑y=21, ∑x

2=14 and ∑xy=46.

54. The values of a and b are respectively (a) 2 and 3 (b) 1 and 2 (c) 2 and 1 (d) 3 and 2 55. The value of y when x=3 is (a) 5 (b) 7 (c) 9 (d) 11

GENERAL APTITUDE



Q.Nos 56 to 60 will carry one mark each 56.A train running at a uniform speed crosses two women coming in the opposite direction at 2.4 kmph and 6 kmph in 45 seconds and 36 seconds respectively . Find the speed of the train ? a.10.8 kmph b. 12 kmph c. 13.2 kmph d. 14.4 kmph 57.A, B and C start a business . A invests 2 times as much as B invests . A and B invests 3 times of what C invests. Then the ratio of capital of A,B and C is ? a.1:3:6 b. 6:3:1 c. 1:2:3 d. 3:2;1 58.A container contains 1000 litres of milk. From this container 100 litres of milk was taken out and replaced by water . If this process was repeated another three times , how much milk is now contained by the container ? a.729 lts b. 700 lts c. 656.1 lts d. 343.9 lts 59.Identify the pair of words , which has a relationship similar to the pair in question Romantic : Realistic a.Dramatic : Prosaic b. Fanciful : actual c. Thought : idea d. Poet : Dramatist 60.This question has a set of four words . Choose the word that does not belong to the group a. Cartridge b. Barrel c. Gun d. Drum Q.Nos 61 to 65 will carry two marks each 61.In the following sentence , some part of the sentence is underlined . Beneath each sentence you will find four ways of phrasing the underlined part. Choose the best choice that follows the requirements of standard written English In the split brain preparation , we have managed to dissociate various parts of the brain from one another a.to associate various parts of the brain from one another b. to dissociate various parts of the brain from one another c. to dissociate various parts of the brain from each another d. to dissociate various parts of the brain among each other 62.A program instituted in a particular state allows parents to prepay their children’s future college tuition at current rates .The program then pays the tuition annually for the child at any of the states public colleges in which the child enrolls . Parents should participate in the program as a means of decreasing the cost of their children’s college education. Which of the following , if true , is the most appropriate reason for parents not to participate in the program ? a.The parents are unsure about which public college in the state the child will attend b. The amount of money accumulated , by putting the prepayment funds in an interest-bearing account today will be greater than the total cost of tuition for any of the public colleges when the child enrolls c. The annual cost of tuition at the states public colleges is expected to increase at a faster rate than the annual increase in the cost of living d. Some of the state’s public colleges are contemplating large increase in tuition next year. 63.This question consists of six statements followed by options consisting of three statements put together in a specific order . Choose the option which indicates a valid argument , that is , where the third statement is a conclusion drawn from the preceding two (A) Navratilova won the tournament (B) Only talented people can win a tournament (C) Graf is not talented (D) Navratilova is not talented (E) Graf lost the tournament (F) Navratilova is more talented than graf a. BAD b. BCE c. DAF d. EAC 64.Rajesh started walking along the boundaries square field from corner point A. After half an hour, he reached the corner point ‘C’ diagonally opposite to A. If this speed was 8 kmph what is the area of the field in square kilometer ? a. 16 b. 4 c. 8 d. none 65.If the price of petrol is increased by 20 % and subsequently by 40 %, what is the final price if the original price is Rs. 25 ? a. 42 Rs b. 21 Rs c. 63 Rs d. 84 Rs



MOCK TEST –I (ECE) KEY

1.b 2.c 3. c 4.d 5.c 6.b 7.b 8.b 9.d 10.b 11.b 12.c 13. a

14.c 15. b 16.c 17.a 18.d 19.d 20.c 21.c 22.d 23.c 24.d 25.c

26.d 27.a 28.c 29.c,b 30.a 31.c 32.c 33.a 34.d 35.b 36.b 37.c

38.b 39.c 40.d 41.d 42.c 43.a 44.d 45.b 46.b 47.a 48.b 49.a

50.d 51.c 52.b 53.d 54.d 55.c 56.b 57.b 58.c 59.a 60.d 61.b

62.b 63.b 64.c 65.a

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