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1

General Aptitude

Q. No. 1 – 5 Carry One Mark Each

1. Five teams have to compete in a league, with every team playing every other team exactly

once before going to the next round. How many matches will have to be held to complete

the league round of matches?

(A) 20 (B) 10 (C) 8 (D) 5

Answer: (B)

Exp: For a match to be played, we need 2 teams

No. of matches = No. of ways of selections 2 teams out of 5 5

2C 10

2. Fill in the blank with the correct idiom/phrase.

That boy from the town was a _____ in the sleepy village.

(A) dog out of herd (B) sheep from the heap

(C) fish out of water (D) bird from the flock

Answer: (C)

Exp: From the statement, it appears that boy found it tough to adapt to a very different

situation.

3. Choose the statement where underlined word is used correctly.

(A) When the teacher eludes to different authors, he is being elusive.

(B) When the thief keeps eluding the police, he is being elusive.

(C) Matters that are difficult to understand, indentify or remember are allusive.

(D) Mirages can be allusive, but a better way to express them is illusory.

Ans: (B)

Exp: Elusive: Difficult to answer.

4. Tanya is older than Eric. Cliff is older than Tanya. Eric is older than Cliff.

If the first two statements are true, then the third statement is:

(A) True (B) False (C) Uncertain (D) Data insufficient

Ans: (B)

5. Choose the appropriate word/phrase, out of the four options given below, to complete the

following sentence:

Apparent lifelessness ___________ dormant life.

(A) harbours (B) leads to (C) supports (D) affects

Answer: (A)

Exp: Apparent: looks like

dormant: hidden

Harbour: give shelter

Effect (verb): results in




2

Q. No. 6 – 10 Carry Two Marks Each

6. A coin tossed thrice. Let X be the event that head occurs in each of the first two tosses.

Let Y be the event that a tail occurs on the third toss. Let Z be the event that two tails

occurs in three tosses.

Based on the above information, which one of the following statements is TRUE?

(A) X and Y are not independent (B) Y and Z are dependent

(C) Y and Z are independent (D) X and Z are independent

Answer: (B)

Exp: Let y as tail occurred in third toss

and z as two tails in third toss which can be {TTH, THT, HTT}

y = {TTH, TTT}

∴ both y and z are dependent.

7. Given below are two statements followed by two conclusions. Assuming these statements

to be true, decide which one logically follows.

Statements:

I. No manager is a leader.

II. All leaders are executives.

Conclusions:

I. No manager is an executive.

II. No executive is a manager.

(A) Only conclusion I follows. (B) Only conclusion II follows.

(C) Neither conclusion I nor II follows. (D) Both conclusions I and II follow.

Answer: (C)

Exp:

Therefore concluding diagram can be

It can be manager that is manager can be executive also.

Some executives are also leaders that is not a manager

Executive

L NL




3

8. In the given figure angle Q is a right angle, PS:QS=3:1, RT:QT=5:2 and PU:UR=1:1. If

area of triangle QTS is 20 cm2, then the area of triangle PQR in cm

2 is ________.

Answer: 280

Exp: Let area of triangle PQR be „A‟

le

SQ 1 1

PQ 1 3 4

QT 2 2

QR 2 5 7

1Area of QTS SQ QT

2

1 1 2

PQ QR2 4 7

1 2 1

PQ QR4 7 2

le1Area of PQR

14

2

2

1given 20cm A

14

A 14 20 280cm

9. Select the appropriate option in place of underlined part of the sentence.

Increased productivity necessary reflects greater efforts made by the employees.

(A) Increase in productivity necessary (B) Increase productivity is necessary

(C) Increase in productivity necessarily (D) No improvement required

Answer: (C)

10. Right triangle PQR is to be constructed in the xy-plane so that the right angle is at P and

line PR is parallel to the x-axis. The x and y coordinates of P, Q, and R are to be integers

that satisfy the inequalities: 4 x 5 and 6 y 16. How many different triangles could

be constructed with these properties?

(A) 110 (B) 1,100 (C) 9,900 (D) 10,000

Answer: (C)

R

TU

P S Q




4

Exp:

1 1

1 1

2 1 2

2 1 2

X 4 X 5

Y 6 Y 16

X 9 chairs X X

Y 10 chairs Y Y

Total triangles 10 11 9 10 9900

Instrumentation Engineering

Q. No. 1 – 25 Carry One Mark Each

1. The capacitor shown in the figure is initially charged to +10 V. The switch closes at time

t=0. Then the value of cV (t) in volts at time t=10 ms is _____ V.

Answer: 3.67

Exp: It is a source free network where capacitor voltage

3

t

c 0

100t

100 10 103

c

V t V e ; t 0

10e

V 10 10 10e 3.67V

1

RC100

2. The voltage 0(E ) developed across a glass electrode for pH measurement is related to the

temperature (T) by the relation

(A) 0 2

1E

T (B) o

1E

T (C) 0E T (D) 2

0E T

Answer: (C)

3. Let 3+4j be a zero of a fourth order linear –phase FIR filter. The complex number which

is NOT a zero of this filter is

(A) 3 4j (B) 3 4

j25 25

(C) 3 4

j25 25

(D) 1 1

j3 4

Answer: (D)

Exp: The property of a FIR filter is that if Zo is a zero then the remaining zeros are

t 0

R 10k C 1 F

cV (t)




5

0

0 0

1 1, Z *, *

Z Z

3 4 3 4j , 3 4j , j

25 25 25 25

So option (D) is not matching with any of this.

4. The bridge most suited for measurement of a four-terminal resistance in the range of

0.001 to 0.1 is

(A) Wien‟s bridge (B) Kelvin double bridge

(C) Maxwell‟s bridge (D) Schering bridge

Answer: (B)

5. A load resistor RL is connected to a battery of voltage E with internal resistance Ri

through a resistance Rs as shown in the figure. For fixed values of L iR and R , the value

of SR 0 for maximum power transfer to RL is

(A) 0 (B) L iR R (C) LR (D) L iR R

Answer: (A)

Exp: When load is constant, we should see for what value of resistance current will be

maximum and LRP max .

6. A mass-spring-damper system with force as input and displacement of the mass as output

has a transfer function 2G(s) 1/ s 24s 900 . A force input F(t)=10 sin(70t) Newtons

is applied at time t = 0s. A beam from an optical stroboscope is focused on the mass. In

steady state, the strobe frequency in hertz at which the mass appears to be stationary is

(A) 5 / (B) 15 / (C) 35 / (D) 50 /

Answer: (C)

iR

ELR

sR




6

7. A light detector circuit using an ideal photo-diode is shown in the figure. The sensitivity

of the photo-diode is 0.5 A / W. With Vr= 6V, the output voltage 0V 1.0 for 10 W

of incident light. If Vr is changed to 3V, keeping all other parameters the same, the value

of Vo in volts is __________ V.

Answer: -1

Exp: Here Vo is independent of the value of Vr

It depends on the intensity of incident light.

8. The logic evaluated by the circuit at the output is

(A) XY YX (B) X Y XY

(C) XY XY (D) XY XY X Y

Answer: (A)

Exp: Output of upper AND gate is XY

Output of lower AND gate is XY

Output of OR gate is XY XY .

9. The value of 2

1dz,

z where the contour is the unit circle traversed clockwise, is

(A) 2 i (B) 0 (C) 2 i (D) 4 i

Answer: (B)

Exp: Given 2

1dz

z where c is unit circle.

Let 2

1f (z)

z

rV

0V

R

Incident

light

X

Y

Output




7

f(z) is not analytic at z = 0

By Laurent series, f(z) can be expressed as

2

1 1f (z) (zero tens) 0. 1.

z z

Analytic part Principal part

Principal part has only two terms

z 0 is pole of order 2

z 0

1Res f (z) coefficient of

z

1b 0

By Cauchy‟s residue theorem

2

1dz 2 i (sum of residues)

z

2 i 0 0

10. Consider the ammeter-voltmeter method of determining the value of the resistance R

using the circuit shown in the figure. The maximum possible errors of the voltmeter and

ammeter are known to be 1% and 2% of their readings, respectively. Neglecting the

effects of meter resistances, the maximum possible percentage error in the value of R

determined from the measurements, is ___ %.

Answer: 3

Exp: x xx x

x x

V V I2%R R 3%

I I 1%

11. The highest frequency present in the signal x(t) is fmax. The highest frequency present in

the signal 2y(t) x (t) is

(A) max

1f

2 (B) maxf (C) max2f (D) max4f

Answer: (C)

Exp: Multiplication in time domain corresponds to convolution in frequency domain

2x t x f *x f

Using limit property of convolution x2(t) have maximum frequency 2fm.

i

Source

V

R

Voltmeter

Ammeter

V




8

12. Let A be an n×n matrix with the rank r 0 r n . Then Ax=0 has p independent

solutions, where p is

(A) r (B) n (C) n-r (D) n+r

Answer: (C)

Exp: Given AX=0

n nA r 0 r n

p = no. of independent solution

i.e nullity = p

We know that rank + nullity = n

r p n

p n r

13. The double integral a y

0 0f (x, y) dxdy is equivalent to

(A) x y

0 0f (x, y) dxdy (B)

a y

0 xf (x, y) dxdy

(C) a a

0 xf (x, y) dxdy (D)

a a

0 0f (x, y) dxdy

Answer: (C)

Exp: Given double integral a y

0 0f (x, y)dx. dy

and x=0 to x=y, y=0 to y=a

the diagram is

By applying change of order of integration

a a

x 0 y xf (x,y)dydx

14. In the circuit shown, the switch is momentarily closed and then opened. Assuming the

logic gates to have non-zero delay, at steady state, the logic states of X and Y are

X Y

1

(0,a)

x 0

(0,0) (a,0)

(a,a)

y x

y a




9

(A) X is latched, Y toggles continuously (B) X and Y are both latched

(C) Y is latched, X toggles continuously (D) X and Y both toggle continuously

Answer: (D)

Exp: The above circuit is a stable multivibrator circuit, where odd numbers of inverter are there

in the loop. In such a circuit, irrespective of the position of output, it always toggles.

Latching means X and Y will be fixed to same value, in this case it is not possible.

15. Consider the logic circuit with input signal TEST shown in the figure. All gates in the

figure shown have identical non-zero delay. The signal TEST which was at logic LOW is

switched to logic HIGH and maintained at logic HIGH. The output

(A) stays HIGH throughout (B) stays LOW throughout

(C) pulses from LOW to HIGH to LOW (D) pulses from HIGH to LOW to HIGH

Answer: (D)

Exp: For analysis point of view, assume delay of each gate is 10 msec. However we can take

any value.

By referring the circuit the upper input to the NAND gate is direct test signal.

The lower input to NAND gate is TEST but with a delay of 30 nsec.

Assuming the delay of NAND gate is 0. First draw output waveform (ideal case) then

shift that by 10 msec. i.e. introduce the delay.

TEST Output

Test

Test

with delay 30nsec

Output with

delay 0

30 nsec0

0

0

Output with

NAND gate

delay 10 n sec40 nsec0 10 nsec




10

So we can clearly say that initial output change from high to low, then it changes from

low to high and then finally at steady state output is 1.

Note: Saying output is high (option A) will be wrong here. We are not interested to find

steady state output.

16. A p-type semiconductor strain gauge has a nominal resistance of 1000 and a gauge

factor of +200 at o25 C. The resistance of the strain gauge in ohms when subjected to a

strain of 410 m m at the same temperature is _________ .

Answer: 1020

Exp:

1

4R R

GF R 200 10 1000

20

p-type semiconductor have a positive gauge factor

i.e., Resistance with in strain

∴ Rstrained = 1000+20 = 1020

17. A system with transfer function 2

1G s

s 1

has zero initial conditions. The percentage

overshoot in its step response is _________ %.

Answer: 100

Exp: Comparing the denominator, 0

21

% Overshoot e 100 100

18. Liquid flow rate is measured using

(A) a Pirani gauge (B) a pyrometer

(C) an orifice plate (D) a Bourdon tube

Answer: (C)

19. The magnitude of the directional derivative of the function 2 2f x,y x 3y in a

direction normal to the circle 2 2x y 2, at the point (1, 1) , is

(A) 4 2 (B) 5 2 (C) 7 2 (D) 9 2

Answer: (A)

Exp: Let 2 2f (x,y) x 3y

Let 2 2x y 2 and P is (1,1)

Normal to the surface

i j

x y

2xi 2yj




11

at (1,1)

2i 2j

Le a 2i 2j

We need to calculate magnitude of directional derivatives of f along a at (1,1)

Magnitude of directional deviations ˆf .a

(1,1)

f ff i j 2xi 6yj

x y

f 2i 6j

a 4 4 2 2

2i 2j i ja

2 2 2

Magnitude of direction derivative i j

2i 6j .2

2 6 8

4 22 2

20. A power line is coupled capacitively through various parasitic capacitances to a shielded

signal line as shown in the figure. The conductive shield is grounded solidly at one end.

Assume that the length of the signal wire extending beyond the shield, and the shield

resistance are negligible. The magnitude of the noise voltage coupled to the signal line is

(A) directly proportional to 1GC

(B) inversely proportional to

the power line frequency

(C) inversely proportional to 15C

(D) Zero

Answer: (D)

~ 1 1V sin t1GC

1SC

SGC

2SC2

Signalline

Conductiveshield

Powerline

1




12

21. The torque transmitted by a cylindrical shaft is to be measured by using two strain gauges.

The angles for mounting the strain gauges relative to the axis of the shaft for maximum

sensitivity are

(A) o45 (B) o60 (C) 90 (D) o180

Answer: (A)

Exp:

22. The output voltage of the ideal transformer with the polarities and dots shown in the

figure is given by

(A) iNV sin t (B) iNV sin t (C) i

1V sin t

N (D) i

1V sin t

N

Answer: (B)

Exp: First mark the mutual voltage polarity using dot convention (when a reference current

enters at dot of one coil, it generates positive polarity on dot terminal of other coil)

2 2

i 1

2 1 i

o 2 i

Using Transformer ratio

V N

V N

NV V NV sin t

1

V V NV sin t

23. The filter whose transfer function is of the form 2

2

s bs cG s

s bs c

is

(A) a high-pass filter (B) a low-pass filter

(C) an all-pass filter (D) a band-reject filter

Answer: (C)

0ViV sin t

1: N

0ViV sin t

1: N

2VV

45

45




13

24. An apparatus to capture ECG signals has a filter followed by a data acquisition system.

The filter best suited for this application is

(A) low pass with cutoff frequency 200 Hz

(B) high pass with cutoff frequency 200 Hz

(C) band pass with lower and upper cutoff frequencies 100 Hz and 200 Hz for its pass band

(D) band reject with lower and upper cutoff frequencies 1 Hz and 200 Hz for its stop band

Answer: (A)

Exp: More appropriate will be a Band pass filter from 1Hz to 200Hz

25. The figure shows a half-wave rectifier circuit with input voltage V t 10sin 100 t

volts. Assuming ideal diode characteristics with zero forward voltage drop and zero reverse

current, the average power consumed in watts by the load resistance RL is ____ W.

Answer: 0.25

Exp: The voltage waveform at R 100 is as shown below.

22

rmsavg

10 2VP

R 100

0.25 Watt

Q. No. 26 – 55 Carry Two Marks Each

26. Consider a low-pass filter module with a pass-band ripple of in the gain magnitude. If

M such identical modules are cascaded, ignoring the loading effects, the pass-band ripple

of the cascade is

(A) M

1 1 (B) M (C) M1 (D) M

1

Answer: A

27. The probability density function of a random variable X is xXp x e x 0 and 0

otherwise. The expected value of the function 3x 4xg x e is ________.

Answer: 4

Exp: Probability density function of X is

V t

LR 100

10




14

x

x

3x

4x

given as P (x) e ; x 0

0 ; otherwise

and g (x) e

x x x0

E g (x) f (x)g (x)dx

3x

x 4

0

3xx

4

0

x

4

0

e e dx

e dx

e dx

x /4

0

e

1

4

4 e 1

4[0 1] 4

28. A system is represented in state-space as X AX Bu, where 1 2

A6

and

1B .

1

The value of for which the system is not controllable is _________.

Answer: -3

Exp: For a system to be uncontrollable, its controllability determinant should be equal to zero.

c ABQ B 0

2 2 2 1

1 2 1 3AB

6 1 6

c

1 3Q B AB 0 6 3 0 3

1 6

29. The Seebeck coefficients, in oV C, for copper, constantan and iron, with respect to

platinum, are 1.9, 38.3 and 13.3 respectively. The magnitude of the thermo emf E

developed in the circuit shown in the figure, in millivolts is __________mV.

constantan

o2T 50 C

copper o1T 0 C

E

o3T 15 C

iron o1T 0 C




15

Answer: 1.236

Exp: Cu Constantan

Cu Constantan

1.9 38.3V 40.2 50 2010 V 2.01mV

40.2 V C

Fe Constantan Fe constantan

out

13.3 38.3 51.6 V C V 51.6 15 0.774mV

V 2.01 0.774 1.236mV

30. The current in amperes through the resistor R in the circuit shown in the figure is

__________.

Answer: 1

Exp: Using supermesh analysis

Mesh 1, 3 form super mesh

1 2 3 2

1 2 3

2I I 2I I 0

2I 2I 2I 0

… (1)

1 3

Writing KCL at Q

I I 1 … (2)

Writing KCL on mesh 2

2 1 32I I I 1 … (3)

Solution Equation 1, 2, 3

1 2 3I 0, I I 1A

Current through R is 3I 1A

Note: Strictly saying it is an ambiguous question as the direction of current is not

mentioned, so it could be –1A as well.

1 R 1

1 1

1V

1A

R 1 1A

1 1

1V

1I

3I

Q

2I

1




16

31. In the circuit shown, the voltage source V t 15 0.1 sin (100t) volts. The PMOS

transistor is biased such that it is in saturation with its gate-source capacitance being 4nF

and its transconductance at the operating part being 1 mA/V. Other parasitic impedances

of the MOSFET may be ignored. An external capacitor of capacitance 2 nF is connected

across the PMOS transistor as shown. The input impedance in mega ohm as seen by the

voltage source is ___________ M .

Answer: 1

32. The probability that a thermistor randomly picked up from a production unit is defective

is 0.1. The probability that out of 10 thermistors randomly picked up, 3 are defective is

(A) 0.001 (B) 0.057 (C) 0.0107 (D) 0.3

Answer: (B)

Exp: p = Probability of a thermister is defective

0.1

q 1 p 1 0.1 0.9

n 10

Let X be random variable which is no. of defective pieces.

Required probability = P(x 3)

10 3 7

3

10 3 7

3

C p q

C (0.1) (0.9)

0.057

33. A liquid level measurement system employing a radio-isotopic is mounted on a tank as

shown in the figure. The absorption coefficient of water for the radiation is 17.7 m . If the

height of water in the tank is reduced from 100 mm to 90 mm, the percentage change in

the radiation intensity received by the detector, neglecting abosroption of the radiation by

air, is ___________%.

V t ~

2nF

SV

PMOS

2k




17

Answer: 8

Exp: General formula for the amount of intensity received , xoI I e

I0 Intensity when absorbing material is nill or empty

absorption coefficient

density of the absorption material

x thickness (or) height of the absorbing, material

By considering the given parameters and neglecting others

Intensity received,

(a) When xheight = 100 mm = 0.1 m

7.7 0.1 0.77

1I e e

(b) When x = 90 mm = 0.9 m

7.7 0.09 0.693

2I e e

So, 2 1

1

I Ichange%change 100 100 8%

Initial I

34. A beam of monochromatic light passes through two glass slabs of the same geometrical

thickness at normal incidence. The refractive index of the first slab is 1.5 and that of the

second, 2.0. The ratio of the time of passage of the beam through the first to the second

slab is _________.

Answer: 0.75

Exp: We know, distance d

timevelocity v

Detector

Source

Water




18

∴ The ratio of the time for 2 slabs 1

2

t

t

1 21 1 1 2

2 2 1 2

2

1

2 2

1 1

1

2

d d becauseof samed v d v

d v v d geometrical thickness

v

v

v

v

1.5

2.0

0.75

NOTE: If a light of velocity “v” is passing through a matter of R.I = 0.7 (say)

Then the final output velocity will be v

0.7

35. In the circuit shown in the figure, it is found that BEV 0.7 V amnd EV 0V. If dc 99

for the transistor, then the value of RB in kilo ohms is __________ k .

Answer: 93

BR

10kEI

10V

EV 0V

10V




19

Exp:

B

B

E B

B

10 0.7I (1)

R

0 ( 10V)I 1 I 10mA

1k

10I mA 99

100

100 A

Put the volume of IB in equation (1), we get

6

B

B

9.3 9.3R 10 93k

I 100

36. The output frequency of an LC tank oscillator employing a capacitive sensor acting as

the capacitor of the tank is 100 kHz. If the sensor capacitance increases by 10%, the

output frequency in kilohertz becomes ________ kHz.

Answer: 95.35

Exp: 1

1f

2 LC

Now C' C 0.1C 1.1C

2

2

1 1 ff

2 LC 2 1.1LC 1.1

100kHzf 95.346 kHz

1.1

37. The resolving power of a spectrometer consisting of a collimator, a grating and a

telescope can be increased by

(A) increasing the angular magnification of the telescope

(B) increasing the period of the grating

(C) decreasing the period of the grating

(D) decreasing the slit-width of the collimator

Answer: (C)

Exp: Resolving power of a grating plate can be increased by increasing the number of slits.

i.e., by decreasing the grating period.

10V

1k EF

EV 0V

BV 0.7V

BR

10V




20

38. A transfer function G(s) with the degree of its numerator polynomial zero and the degree

of its denominator polynomial two has a Nyquist plot shown in the figure. The transfer

function represents

(A) a stable, type-0 system (B) a stable, type-1 system

(C) an unstable, type-0 system (D) an unstable, type-1 system

Answer: (D)

Exp: Consider the Transfer function to be

22 2

1

1G s

s s 1

1 1Magnitude M

11

Phase 270 tan

0 M , 270

M 0, 270 90 180

∴ our assumption of G(s) is true

The system is type-1 and is unstable.

39. For the circuit shown in the figure, the rising edge triggered D-flip flop with asynchronous

reset has a clock frequency of 1 Hz. The NMOS transistor has an ON resistance of 1000

and an OFF resistance of infinity. The nature of the output waveform is

0

lm G j

5j

4 j

3j

2 j

1j

1j0.20.3 0.1 0.1

0 Re G j

1 A

2 F 0.1V

SVHIGH

CLKR

Q

QD

Output

NMOS

0




21

A

B

C

D

Answer: (A)

Exp: Before solving the problem, consider the following fact.

clock is +ve edge triggered and input to D flip-flop is constant i.e logic 1.

Reset pin of Flip flip is active high and it can function at any moment of time

independent to clock. Also note that reset will be triggered when V terminal voltage just

crosses 0.1 V.

N-MOS behave as open switch (off state, R ) when Q 0 and it will behave as a

resistance of 1000 when Q 1 (as ON resistance is specified).

Now for analysis, assume capacitor is initially uncharged and a +ve edge is triggered

to D-flipflop, as its input is high. Then Q=1 and Q 0 .

* When Q 0 , N-MOS is off, assuming the input resistance of comparator infinite. Then

the source current can flow only through the capacitor. Now we have to see how much

time the capacitor will take to reach 0.1 V. So that V V and R will change from 0 to 1

and as the reset terminal will be triggered the state of flip-flop changes i.e. Q 0, Q 1 .

and N-MOS gets ON. As the integration of step is ramp if we integrate the constant

current voltage will be ramp.

For this use the capacitor voltage equation.

t

c c0

t6

6 0

1V (t) i d

C

10.1V 1 10 d

2 10

t0.1 t 0.2sec 200 millisec

2

0V

1 A

2 F

0V




22

So at t = 0.2sec, N-MOS is ON. Now the circuit is equivalent to a current source

connected to a parallel combination of RC with non zero initial voltage of capacitor

(0.1V).

Now the capacitor will discharge from its initial voltage with time constant RC 2ms

and at 10 it will react steady state i.e., at 20 m.sec. The nature of discharge is

exponential decay.

So we can conclude from the above analysis that capacitor takes 200 msec to charge upto

0.1V and 20 msec to discharge to the steady state value.

So if the +ve edge of clock appeared at t = 0 then at 200 msec it completed its charging

and at 220 msec it completed its discharging. This continues in each clock cycles.

The following waveform gives further clarity as CLK CLKf 1Hz, T 1000ms

40. Consider the circuits shown in the figure. The magnitude of the ratio of the currents, i.e.,

|I1/I2|, is _____________.

Answer: 1

Exp: By reciprocity theorem, I1 = I2

5

2V2V

5 34

43

2I1I

1 A

2 F

sV

1000

500 msec500 msec

CLOCK

Output

200 msec 20 msec

Charging (Ramp) Discharging

(exp decay)

Q

0.1V

Reset




23

So 1

2

I1

I

41. The linear I-V characteristics of 2-terminal non-ideal dc sources X and Y are shown in the

figure. If the sources are connected to a 1 resistor as shown, the current through the

resistor in amperes is _________A.

Answer: 1.75

Exp: The transfer characteristic curve and the circuit of a non ideal source is given below.

Comparing the curve of X and Y

we can conclude that

x x

y y

X : V 4V, R 2

Y : V 3V, R 1

When we connect these the circuit becomes,

1

4 3I 1.75A

2 1 1

42. The figure shows a spot of light of uniform intensity 50 W/m2 and size 10mm×10 mm

incident at the exact centre of a photo-detector, comprising two identical photo-diodes D1

and D2. Each diode has a sensitivity of 0.4 A/W and is operated in the photoconductive

mode. If the spot of light is displaced upwards by 100μm, the resulting difference

between the photocurrents generated by D1 and D2 in micro amperes, is _________ μA.

SourceY

SourceX

Voltage V

Current A

1

2

3

0

0 1 2 3 54

SourceX

SourceY

1

1

xV 4V

YV 3V

rR 1 xR 2

sV

s

s

V

R

s

1Slope

R

V

I

sV

sR




24

Answer: 40

Exp: Total illuminated Area = 10×10×10-6

m2 = 10

-4m

2

Light power = 50×10-4

W = 5mW

Output from both diodes = 0.4×5mA = 2mA

So output from each diode = 1mA

In second case,

Area of one diode (D1) = 10×5.1×10-6

= 0.51×10-4

m2

Light output (D1) = 0.51×10-4

×50W

= 2.55 mW

Current in D1 = 2.55×0.4 = 1.02 mA

Current in D2 = Total current – ID1

= 2-1.02 = 0.98 mA

D1 D2I I 1.02 0.98 mA 0.04mA 40 A

1D

2D

Photo-

detector

10mm

10mm

Spot of

light




25

43. An ADC is interfaced with a microprocessor as shown in the figure. All signals have been

indicated with typical notations. Acquisition of one new sample of the analog input signal

by the microprocessor involves

(A) One READ cycle only

(B) One WRITE cycle only

(C) One WRITE cycle followed by one READ cycle

(D) One READ cycle followed by one WRITE cycle

Answer: (C)

44. In the figure shown, RT represents a resistance temperature device (RTD), whose

characteristic is given by RT = Ro (1+αT), where R0 = 100, α = 0.0039℃-1 and T denotes

the temperature in ℃. Assuming the op-amp to be ideal, the value of V0 in volts when T =

100℃, is _________V.

Answer: 1.39

Exp: Using the above information

1V 1V

TR

100

0V

Data linesD0toD7

Address

Decode

Logic

D7

D0

Enablebuffers

Start conversion

Endof conversion

Data

Bus

Address

Bus

D7

D0

RD

15A

0A

WR

INT

Analog

Input

ADCMicroprocessor




26

T oR R 1 T

100 1 0.0039 100 139

Since it is a non inverting amplifier its output voltage w.r.t ground is

fi

i

R 1391 V 1 2.39V

R 100

But here Vo is not w.r.t ground, it is across RT

So oV 2.39 1 1.39V

45. The signal x[n] = sin(πn/6)/(πn) is processed through a linear filter with the impulse

response h[n] = sin(cn)/(πn) where c>π/6. The output of the filter is

(A) sin(2cn)/(πn) (2) sin(πn/3)/(πn)

(C) [sin(πn/6)/(πn)]2

(D) [sin(πn/6)/(πn)]

Answer: (D)

Exp:

sin n sin n sin n

n n n

where min ,

Output g n x n *h n

In frequency domain they will be multiplied.

46. If the deflection of the galvanometer in the bridge circuit shown in the figure is zero, then

the value of Rx in ohms is ________ . .

Answer: 33.33

Exp: When the current through galvanometer is 0 then its 2 end voltage are same or we can say

the open circuit voltage across galvanometer is 0.

100 200

100 xR

100

G50

2V

100




27

By voltage division, a

b x

x

V 0.5V

2V R

100 R

Va = Vb

x

x x x

x

2R1 100100 R 4R R 33.33

2 100 R 3

47. In the circuit shown in the figure, both the NMOS transistors are identical with their

threshold voltages being 5V. Ignoring channel length modulation, the output voltage Vout

in volt is ___________V.

Answer: 20

Exp: GS1 GS2V V (Both are identical transistors)

out

out

30 V 10 0

V 20V

30V

10V

NMOS

NMOSoutV

100 200

100xR

100

2V

aV

bV

100

100

100

200

100

xR

100

aV

bV

2V




28

48. In the potentiometer circuit shown in the figure, the expression for Vx is

(A) (1-2α)V (B) (1-α)V (C) (α-1)V (D) αV

Answer: (A)

Exp: Writing KVL as per the current direction

x

2VV R V 0

R

49. An opamp has ideal characteristics except that its open loop gain is given by the

expression AV(s) = 104/(1+10

-3s). This op-amp is used in the circuit shown in the figure.

The 3-dB bandwidth of the circuit, in rad/s, is

(A) 102 (B) 10

3 (C) 10

4 (D) 10

6

Answer: (D)

Exp: Closed loop transfer function ACL

OLCL

OL

AA

1 A

Here 4

iOL 3

i f

R10 1A , 0.1

1 10 s R R 9 1

1V

0V

9k

1k

VA

V VR

R

xV

R

R

xV

V

V

2V

R




29

4

43

CL 4 3 3

3

3 6

6

10

101 10 sA10 0.1 1 10 s 10

11 10 s

10 10

s10 10 s 11

10

In a first order transfer function k

1 s

the bandwidth of system is given by 1

6B.W 10

50. A signal is band-limited to 0 to 12 kHz. The signal spectrum is corrupted by additive

noise which is band-limited to 10 to 12 kHz. Theoretically, the minimum rate in kilohertz

at which the noisy signal must be sampled so that the UNCORRUPTED PART of the

signal spectrum can be recovered, is _________ kHz.

Answer: 22

Exp:

The signal is corrupted from 10 to 12 kHz. So the ideal sampling,

s s

n

X (f ) X f nf

If Fs= 20 kHz then the spectrum will be

So the overlapping is starting from 8 kHz onwards, but we want it should be from 10 kHz

onward because the uncorrupted is up to 10 kHz.

So the sampling frequency should increase by 2kHz.

So sf 20 2 22kHz, the spectrum.

32 8 8 1212 32

12 10 10 12




30

51. The circuit shown in the figure is in series resonance of frequency fc Hz. The value of Vc

in volts is _____________V.

Answer: 100

Exp: Under series resonance condition, voltage across L, C is Q times of the supply voltage.

CV QV

6

c

1 L 1 0.1Q 100

R C 10 0.1 10

V QV 100 1 100V

52. The fundamental period of the signal 2 t

x t 2cos cos t ,3

in seconds, is

__________s.

Answer: 6

Exp:

0

H.C.F 2 ,

L.C.M 3,1 3

2

T 6 secT 3

53. The open loop transfer function of a system is 2

2

s 6s 10G s .

s 2s 2

The angles of arrival

of its root loci are

(A) 4

(B)

3

(C)

2

(D)

5

6

Answer: (A)

10 0.1H

0.1 F CV

c

1V

f Hz

32 10 1212 3410




31

Exp: Angle of arrival is calculated on a complex zero and it is given by,

a 180 GH at a ve imaginary zero

s 3 i s 3 iG s

s 1 i s 1 i

3 i 3 i 3 i 3 i 2iG 3 i

3 i 1 i 3 i 1 i 2 2i 2

o o 1 o

o o o o o

2G 3 i 90 180 tan 180

2

90 180 45 180 135

a 180 135 454

Other angle will be same with opposite sign 4

54. The z-transform of x[n] = a|n|

, 0<|α|<1, is X(z). The region of convergence of X(z) is

(A) 1

z

(B) |z|>a

(C) 1

z

(D) 1

z min ,

Answer: (A)

Exp: n

n n 1x n u n u n 1

1z ; z

x x 1




32

55. The number of clock cycles for the duration of an input pulse is counted using a cascade

of N decade counters (DC 1 to DC N) as shown in the figure. If the clock frequency in

mega hertz is f, the resolution and range of measurement of input width, both in μs, are

respectively

(A) N2 11

andf f

(B)

N10 11and

f f

(C) NN 10 110

andf f

(D)

NN 2 12and

f f

Answer: (B)

Exp:

The Resolution (R) is the smallest change that is detectable.

CLK

1R T

f MHz

Range of measurement of input width = T

N digitdisplay

N digit register LATCH

Clock

Generator

DC1

E R

DC2

E R

DC N

E R

Pulse

shaping

Input pulse

E R :Enable Reset

CLKT

T

Input pulse

Clock pulse




33

NCLK

N

T 10 1 T

10 1T

f

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