EC-2007 ISRO solved paper

8/2/2019 EC-2007 ISRO solved paper

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Electronics - 2007 _ _ $et::-B _

1 With fixed value capacitor C and variable voltage V across it, the energystored in the capacitor isa) CV 2 I < E 1 > P . S C V 2 c) 2 CV 2 d) CV

2 A dc voltage V is applied to a series RL circuit. The steady state currentisa) VIR b) V/L ~ero

3 The time-constant of the networkshown in the figure is

~R b) 2CR , CRc)-4 d) CR-24 In the ideal Op-amp circuit shown,Vois

a) 2v, b) -2 v. d) -3 v,5 If the unit step response of a system is a unit impulse function, then

the transfer function of such a system will bea) 1 b)! I~ f d)_ls S2

~ Three resistors of 6 n each are I~onnected as shown in thefollowing fig. The equivalent 0I

{)resistance between X1 and X2 is x, )(2

a)20 b)40 c) 80 ~20

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7 The source in the circuit shown isa sinusoidal source. The supplyvoltages across various elementsare marked in the figure. The inputvoltage is

a) 10 V ~5V c) 27V d) 24 V8 Laplace transform of e-al J(t) is

a) Ftsye:" b) F(s - a) 10IF(s+a) d) F(s) +as

9 Cos O Can be represented bya) e+i8 _e-i8 b) ei8 _e-i8

2 2i10 Of the following transfer function of second order linear time-invariant

systems, the underdamped system is represented bya) H(S) - 1 b) H(S) _ 1S 2 +4S +4 S 2 +5S +4

1 ~ 1c)H(S)= S2 +4.5S+4 ~.L(S)= S 2 +3S+4

11 A differential amplifier has a differential gain of 20,000.CMRR = 80 dB.The common mode gain is given byI~~ b) 1 c) % d) 012 Two bulbs marked 200 watt - 250 volts and 100 watt-250 volts are

joined in series to 250volt supply. Power consumed in circuits isa)33 watt l ~ p 7 watt c) 100 watt d) 300 wattI~ I The 6 V zener diode shown in thefigure, has zero zener resistanceand a knee current of 5mA. Theminimum value of R so that thevoltage across it does not fall '1o:~'~'. 'below 6 V is

a) 1.2k ohms 1 < ; 9 ) 1 8 0 ohms c) 50 ohms d) 0 ohms

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50n +~ I A zener diode in the circuit shownin the figure below, has a kneecurrent of SmA, and a maximumallowed power dissipation of 330mW. What are the minimum andmaximum load currents that canbe drawn safely from the circuit,keeping the output voltage Vo at6V?a) 0 mA, 180 rnA~10 rnA, 55 rnAI { ) I The voltages at V1 and V2 of thearrangement shown in the figure willbe respectively

I ~V and 5.4 Vb) 5.4 V and 6 Vc) 3 V and 5.4 Vd) 6 V and 3 V

A 24V, 600 mW,Zener diode is to beused for providing a 24 V stabilizedsupply to a variable load. Assumethat for proper Zener action, aminimum of 10 rnA must flowthrough the Zener. If the inputvoltage is 32 V, what would be thevalue of R and the maximum loadcurrent?a) 320 Q, 10 rnA~400 Q, 10 mA

+'9V+

b) 5 rnA, 110 rnAd) 60 rnA, 180 rnA+f,V

~ ~ ~ ~ ~ - - - - - ~6V10 K

. +3\'

'. '., R '. .

.~32V ...R~.

~400Q, 15mA~20Q, 15mA

17 A half - adder can be constructed using two 2-input logic gates. Oneofthem is an AND-gate,the other isa) OR b) NAND c) NOR ~X-OR

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18 For one of the following conditions, clocked J-K flip-flop can be used asDIVIDE BY 2 circuit where the pulse train to be divided is applied atclock input.a) J = 1, K = 1 and the flip-flop should have active HIGH inputsb) J = 1, K = 1 and the flip-flop should have active LOW inputsc) J = 0, K = 0 and the flip-flop should have active HIGH inputs1 < e D 1 J = 1, K = 1 and the flip-flop should be a negative edge triggered one

19 Number of comparators needed to build a 6-bit simultaneous AIDconverter islp3 b)64 c) 7 d)6

20 The AID converter used in a digital voltmeter could be (1) successiveapproximation type (2) Flash converter type (3) Dual slope convertertype. The correct sequence in the increasing order of their conversiontime taken isa) 1,2,3 b)2,1,3 c) 3,2,1 I~,1,2

21 The circuit is a ~:D :D1 " : ' Q1 -_ _ - - - - _ , ._ ~ Qa) Monostable MVc) Adder

b) Astable MV

h ~ D p R FF22 Which of the following binary number is equal to octal number 66.3a) 101101.100 b) 1101111.111 c) 111111.1111 l~r10110.011

23 The Boolean expression for theoutput of the logic circuit shownin the figure is

a) Y = AB_+ A ! ! + Cc)Y = A B + AB + C [2]y = A B +AB + C_ -d)Y = AB + AB + C

24 For the identity AS + A C + BC = AS + A C, the dual form isa)

~d)

- -(A+B) (A +C)(B+C) = (A+B) (A +C)(A + B) ( A + C ) (B+ C ) = (A+ B) (A + C)(A+B) (A +C) (B+C) = (A + B) (A+ C)AB+AC + BC = AB+AC



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I ~ I The logic cir~uit given below converts a binarycode Y 1 Y Z Y 3 into

a)Excess-3 codec)BCD code b) Graycoded)Hammingcode

26 A 4-bit presetable UP counter has preset input 0101. The presetoperation takes place as soon as the counter reaches 1111. Themodulus of the counter isa)5 l ~ r O c)11 d)15

27 A 4-bit synchronous counter uses flip-flops with propagation delay timeof 25 ns each. The maximum possible time required for change of statewill be1


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A sample-and-hold (StH) circuit, having a holding capacitor of 0.1nF, isused at the input of an ADC (analog-to-digital converter). Theconversion time of the ADC is 1 J .l sec, and during this time, thecapacitor should not lose more than 0.5 % of the charge put across itduring the sampling time. The maximum value of the input signal to theStH circuit is 5V. The leakage current of the StH circuit should be lessthana) 2.5m A b) 0.25 mA c) 25.0 J .l A 1~.5 J .l A

32 Determine the output 1001 ~ c) 5 d) Noneof these

37 VSWR of a transmission line is alwaysa) Less than unity ~reater than unityc) Zero ~nfinity

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38 Waveguide acts like af@1Highpass filter~ All pass filter

b) Lowpass filterd) Band reject filter

39 The wave length of a 100MHz electromagnetic wave propagatingthrough a perfect non magnetic dielectric with relative permittivity 8 =9isa) 3 mtrs b) 3 cms 1>j100cms d) 10cms

40 TEMmode exists ina)A circular wave guideIfD~ co-axial cable

b)A rectangular wave guided)Noneof the transmission lines

41 The signal received from a circularly polarized signal by an antenna withlinear polarization compared to the signal received by same circularlypolarized antenna will bea) Maximum b) Zero 1013 dB less d) 3 dB more

42 When the antenna diameter is doubled, the gain of the antennaa) Reduces by half ~Increases by 3 dBc) Reduces by 3 dB ~Increases by 6dB

43 Intrinsic impedance of free space is given asa)75Q b)73Q 1~~77Q d) 300Q

44 Mark the incorrect relationa) D = 8E b) B = J . 1 H c) J = aE

45 If the PRF is 1200 and the pulse width is 1.5 J . L S , the duty cycle will bea) 12.5percent b) 8 percent IfDP.18 percent d) 0.12 percent

46 When VSWR is 3, reflection coefficient is:~~ b)1 c)O d) _ !_4

47 Which transmission line is ideal for handling high power?r1Coaxialline b) MicrostripgStrip line d) Rectangular waveguide

49 Capture effect is a characteristic ofI~~M system b) FM system c) PCMsystem d) TOMsystem



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50 In a band limited channel higher bit rate can be transmitted witha) BPSK~PSK c) FM d) FSK

51 In a transmission line terminated with a load equal to the characteristic~edance, the reflection coefficient is~ero b) +1 c) -1 d) Infinity

52 Poynting vector P = Ex H has the unit1IWatts/metre2 b)Watts/metre c)Watts-metre d)Watts-metre2

53 If 1watt of RF power is fed to a directional coupler having 30dB coupling,the power available at the coupled port is

1 1 1 ~ 1a)-w b)-w c)-w @>--w30 10 100 1000~~I The following demodulator scheme requires least E bNo

a) BPSK b) FSK c) ASK d) QAM55 The channel capacity under the Gaussian noise environment for a

discrete memoryless channel with a bandwidth of 4 MHz and SNR of 31 isI > ~ O Mbps b)4 Mbps c) 8 Kbps d) 4 kbps .ICfWISatellite channel can beattributed

a)Onlybandwidth limitedc) Bothbandwidth& power limited

1 ( 6 ) 1Onlypower limitedd) Noneof the above

57 A unit vector perpendicular to the vectors I i = 2i - 3 j + k and b = i + j - 2k ,isa) ~(-i+ j+k)

1 @ 1 ~ ( i + j+k)b) Jx(i+j-k)d) (i+ j+k)

58 The region of the z plane for which I z - a l = 1(Re " * 0)isz+aa)x-axis 1~ly-aXiSc)Thestraight line z = JaJ None of the aboveIf o c, f J ' yare the roots of equations x3+ PX2+QX+!J=O f59 Then the value of tan" oc+tan-1 f J + tan-1y isa) nn] 2 ~nTr c) Znr: d) nTr4



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1 a b+cThe value of the determinant 1 b c+a is60 1 c a+b

~o b) 1 c) (a+b+c) d) 361 I I dxdThe value of f f Y is

o 0 ~(1-x2)(1- y2)b) Jr4

Jr2a)-2 d) Jr262 Solution of (D2 + 16)y = cos4x, is

a) y = Acos4x +Bsin 4x+_!_cos4x8c) y =Acos4x+ Bsin4x+_!_sin4x8

b) y = Acos4x+ Bsin4x+~sin4x8i@ly=ACOS4x+Bsin4x+;coS4x

63 Laplace transform of t2 +2t+3 is-2 2 3a) -----S3 S2 S

~+2+~S3 S2 S

2 2 3b) -+--_S3 S2 S-2 2 3d) -+---S3 S2 S

64 Equation of a straight line passing through the point (-1,2) and makingequal intercepts on the axes isa) x-y=l b) x-2y=1 l < ? D f + y=l d) x-y=2

65 A bag contains eight white and six red marbles. The probability ofdrawing two marbles of same colour is) 8c26c2 I d T h l 8c2 . 6c2a @-+-14c2 14c2 14c2c) 8c26c2 d) 8c2 + 6c2

14c2-14c2 14c2 12c2

I~ IThe Algebraic multiplicity of the matrix A ~ [~ ~3 I } sa) 1 b) 2 c) 3 d) 4



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67 The impedance of an inductive reactance variesa) Linearlywith frequencyb) Parabolicallywith frequencyc) Exponentiallywith frequencyI ~ I Linearlywith frequencyin an increasingmanner

68 Two resistance R1and R2give combined resistance of 4.5 ohms when inseries and 1 ohm when in parallel. The resistances are~ 3 ohms and 6 ohms b) 3 ohms and9 ohms~1.S ohms and 3 ohms d) 1.SohmsandO.Sohms

69 Which of the following bulbs will have the least resistance?a)220V, 60W b) 220V, 100Wc) 11SV,60W l~r1S V, 100W

70 A resistance of 5 ohms is furtherdrawn so that its length becomesdouble. Its resistance will now bea)Sohms b) 7.Sohms 10110 ohms d) 20 ohmsThe power rating of a 470 ohm resistor carrying a current of 40mAshould bea) Y 4 W b)%W c) 2 W d) 1W

72 Equivalent Resistance between Xand Y is

750X 500

y250

~7SQ b) SOQ c) 27SQ d)Noneof above73 The open-circuit emf of a storage cell is 2.2 volts. The terminal voltage

measured when the current is 12A is found to be 1.98 volts. Theinternal resistance of the cell isa)0.00183ohm l@)p.0183ohm c)0.183ohm d) 1.83ohm

74 A capacitor passes a current of 12.6 rnA when supplied with 20 V acwith a.frequency of 1kHz. The capacitance of the capacitor is110.1!lF b)0.1pF c)1!lF d)1F

75 The system response can be tested ~er witha)Sinusoidal inputsignal @Unit impulse inputsignalc)Ramp input signal d) Exponentiallydecayingsignal

76 In an ideal op-amp the output impedance isa) SOohm b) 100ohm c) Infinite I ~ e r o



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77 What will be dB gain for an increase of power level fro~ to 26W~1 ~2 ~8 ~

78 The oscillator with the best frequency stability and accuracy isa) Hartley oscillator ~~olpitts Oscillatorc) Tickler feedback oscillator ~rystal controlled oscillator79 The desirable properties of transformer core material area) Low permeability and low hysteresis lossHigh permeability and high hysteresis lossHigh permeability and low hysteresis lossLow permeability and high hysteresis loss80 The quality factor of series R-L-C circuit will increase ifI1R decreases. , b) R increases.CYVoltage increases. d) Voltage decreases.


EC-2007 ISRO solved paper

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