EC

1. When a inductive coil connected to a 200 V, 50Hz ac supply with 10A current flowing through it dissipates 1000 watts then which of the following will have least value in ohms-

a.) Resistance

b.) Reactance

c.) Impedance

d.) None

2.

Oscillator crystal are made of –

a.) Silicon

b.) Germanium

c.) Quartz

d.) None3.

For small size, high frequency coils, the most common core material is-

a. )Air

b. )Ferrite

c.) Powdered ion

d.) Steel4.

If we have a parallel plate capacitor of plate area ’A’ and plate separatoin t and having a capacity C and a metallic plate r of area A and of negligible thickness is introduced in thecapacitor at a distance from either of the two plates as shown in the given figure then the capacity of the capacitor will become –

a.)

b.) C

c.) 2C

d.) 4C5.

A superconductor is a –

a.) A material showing perfect conductivity and Meissner effect below a critical temperature

b.) A conductor having zero resistance

c.) A perfect conductor with highest di-magnetic susceptibility

d.) A perfect conductor which becomes resistance when the current density through it exceeds a critical value

6.

When an inductor tunes at 200 KHz with 624 pF capacitor and at 600 KHz with 60.4 pF capacitor then the self capacitance of the inductor would be –

a) 8.05 pF

b) 10.05pF

c.) 16.01pF

d.) 20.01pF7.

Sparking occur when a load is switched off because the circuit has high –

a.) Inductance

b.) Capacitance

c.) Resistance

d.) None8.

Sparking between contacts can be reduced by inserting a –

a.) Resistance in the line

b.) Capacitor in series with contacts

c.) Capacitor in parallel with contacts

d.) None9.

RF amplifier of an A.M. receiver is normally biased in –

a.) Class ’A’

b.) Class ’b’

c.) Class ’C’

d.) None10.

The value of gate voltage for the operation of enhancement of only N channel MOSFET has to be –

a.) High positive

b.) High negative

c.) Low positive

d.) Zero11.

The input gate current of a FET is –

a.) a few microamperes

b.) negligibly small

c.) a few milliamperes

d.) a few amperes12.

In the following fig. with R = 30k, the value of current through 2 K resistor is –

a.) 25 mA

b.) 40 mA

c.) 25/16 mA

d.) 10 mA13.

A step recovery diode –

a.) has on extremely short recovery time

b.) conducts equally well in both directions

c.) is mainly used as a harmonic generator

d.) is an ideal rectifiers of high frequency signals14.

In order to get maximum undistorted output signal from CE amplifier with VCC 10V, the value of VCE (Q) should be approximately-

a.) 0.1V

b.) 5V

c.) 10V

d) V15.

In a FET the electrode, which corresponds to collector in bipolar transistor, is –

a.) source

b.) drain

c.) gate

d.) none16.

The device which acts like an NPN and a PNP transistor connected base to base and emitter to collector is –

a.) Triac

b.) UJT

c.) Diac

d.) SCR17.

A typical optical fibre has –

a.) High refractive index core and low refractive index cladding

b.) Low refractive index core and high refractive index cladding

c.) Both a and b

d.) None18.

In the following figure circuit diagram of an op-amp based is shown. The ratio is equal to –

a.) 9

b.) 11

c.) 10

d.) 2119.

When a loud speaker is connected across the terminals A and B of the network shown in the fig. then its impedance to obtain maximum power dissipation in it will be –

a.) 3 – j1

b.) 3 + j9

c.) 7.5 + j 2.5

d.) 7.5 – j 2.520.

In the lattice network, the value of R for the maximum power transfer to the load –

a.) 5

b.) 6.5

c.) 8

d.) 9

21.

For a lossy transmission line short circuited at the receiving end, the input impedance is given by (Z0 is the characteristic impedance, Ö is the propagation constant and l is the length of the line-

a.) Z0 cot h Öl

b.) Z0 cot Öl

c.) Z0 tan h.Ö l

d.) Z0 tan Öl22.

The approximate thickness of the radome wall should be –

a.) l

b.) l/4

c.) l/2

d.) l/823.

A relatively permanent information is stored in

a. ) ROM

b.) RAM

c.) PROM

d.) Volatile memory

24.

The rise time of the RC network shown in the given figure is approximately equal to –

b.) RC

c.) 2RC

d.) 4RC25.

If in the network shown in the fig. initially a steady state is attained by closing the switch ’s’ and then if the switch is opened at t = 0, then thecurrent i(t) through the inductor will be –

a.) cos50tA

b.) 2A

c.) 2cos100tA

d.) 2sin50tA26.

When the p network of figure – I and T-network of figure – II are equivalent then the values of R1, R2 and R3 will be respectively –

a) 9W, 6W and 6W

b.) 6W, 6W and 9W

c.) 9W, 6W and 9W

d.) 6W, 9W and 6W27.

When the impedance matrices of a two port networks are given by and , then if these two networks are connected in series then the impedance matrix of the resulting two-port network will be –

d.) indeterminate28.

Joule/coulomb is the unit of -

a.) Electric field potential

b.) Potential

c .) Charge

d.) None of the above29.

The electric field line and equipotential lines-

a.) Are parallel to each other

b.)Are one and same

c.) Cut each other orthogonally

d.)Can be inclined to each other at any angle30.

For a lossy transmission line short circuited at the receiving end, the input impedance is given by (When Z0 is the characteristic impendence g is the propagation constant and L is the length of the line

31.

When two equal positive point charges are placed along X- axis at X1 and –X1 respectively then the electric field vector at a point P on the positive Y-axis will be directed-

a.) In the +x direction

b.) In the –x direction

c. ) In the +y direction

d.) In the –y direction32.

The directions of and in TEM mode transmission line with respect to the direction of propagation are-

a.) Both and are transverse to the direction of propagation

b.) is and are transverse and h has a component in the direction of propagation

c.) is entirely transverse and has a component in the direction of propagation

d. ) is entirely transverse and has a component in the direction of propagation33.

The lowest TM mode in a rectangular waveguide of cross –section a x b with a>b will be-

a.) TM01

b.)TE10

c.) TM112

d.)TE11

34.

When a transmitter in a free space radiates a mean power of ’p’ watts uniformly in all directions then at a distance d sufficiently far from the source in plane the electric field E should be related to p and d as –

35.

. When a dipole antenna was radiating with some excitation in free space radiating a certain amount of the power v if then this antenna is immersed in a lake where water is non-dissipative but has a dielectric constant of 81, then the radiated power with the same

excitation will be

a.) Decrease to finite non-zero value

b.)Remain the same

c. )Increase

d.)Decrease to zero36.

When a (75 – j40)W load is connected to a coaxial line of Z0 = 75 W at 6MHz then the load matching on the line can be accomplished by connecting-

a.) A short – circuited stub at the load

b.)An inductance at the load

c. )A short circuited stub at a specific distance from the load

d.)none of the above37.

As compared to analog multimeters, digital multimeters are –

a.) less accurate

b.) more accurate

c.) equally accurate

d.) none.38.

When a signal of 10 mV at 75 MHz is to be measured then which of the following instruments can be used –

a.) VTVM

b.) Cathode ray oscilloscope

c.) Moving iron voltmeter

d.) Digital multimeter39.

Which of the following statement is true about two wattmeter method for power measurement in three phase current ?

a.) power can be measured using two wattmeter method only for star connected three phase circuits.

b.) when two meter show indentical readings, in the power factor is 0.5.

c.) when power factor is unit, one of the wattmeter reads zero

d.) when the reading of the two wattmeters are equal but of opposite sign, then the power factor is zero –40.

When a capacitance transducer has two plates of area 5cm2 each, separated by an air gap of 2mm than the displacement sensitivity in pf/cm due to gap change would be –

a.) 11.1

b.) 44.2

c.) 52.3

d.) 66.341.

The Q of a radio coil –

a.) is independent of frequency

b.) increases monotonically as frequency increases

c.) decreases monotonically as frequency increases

d.) increases upto a certain frequency and then decreases beyond that frequency42.

When a generator of internal impedance and operating at 1GHz feeds a load via a coaxial line of characteristic impedance 50 ohm then the voltage wave ratio on the feed line is –

a.) 0.5

b.) 1.5

c.) 2.5

d.) 1.7543.

The coding system typically used in digital telemetry is –

a.) PPM (pulse position modulation)

b.) PAM (pulse amplitude modulation)

c.) PCM (pulse code modulation)

d.) PDM (pulse duration modulation)44.

Radiation pyrometers are used for the measurement of temperature in the range of –

a.) -2000C to 5000C

b.) 00C to 5000C

c.) 5000C to 12000C

d.) 12000C to 25000C45.

In the given figure band structure is shown. It is of –

a.) Gallium Avesenide (GaAs)

b.) Silicon (Si)

c.) Copper (Cu)

d.) Germanium (Ge)46.

When anode is positive with respect to cathode in an SCR, the numbers of blocked p-n junction is –

a.) 1

b.) 2

c.) 3

d.) 447.

The circuit symbol for a GTO is

a. b.

c. d.

48.

In the given fig. mark out the type of Cyclo converters

a.) 1 phase to 1 phase with continuous conduction

b.) 1 phase to 1 phase with discontinuous conduction

c.) step up device

d.) 3 phase to 1 phase device

In the given fig. A-1, C=5, m H and C=20 m F, C is initially charged to 200 V. After the switch.

S is closed at t = 0 the

maximum value of current and the

time at which it reaches this value are respectively.

a.) 400 A, 15.707 mS49.

b.) 50 A, 30 mS

c.) 100 A, 62.828 mS

d.) 400 A, 31.414 mS

50.

50. In the given circuit the maximum current in the main SCR M can be-

a.) 200 A

b.) 170.7 A

c.) 141.4 A

d.) 70.7 A

51.

The transfer function of an amplifier is given by

The high 3-db frequency of the amplifier will approximately

a.) 5850 KHZ

b.)585 KHZ

c.) 5850 HZ

d.)585HZ

52.

In comparison to full wave rectifier with two diodes the four divide bridge rectifier has the dominant advantage of -

a). Higher current carrying

b.)Lower ripple factor

c.) Higher efficiency

d.)Lower peak increase voltage require

53.

Power output increase in a class-c amplifier-

a.) If the conduction angle decrease

b).If the conduction angle increase

c.) Are not governed by the conduction angle

d.)None of the above54.

A transistor with hie = 1.5 k and hfe = 75 is used in an emitter follower circuit where R1 and R2 are used for normal biasing . Approximate value of it’s current amplification is-

a.)75

b.)76

c.)75/76

d.)-7555.

Amplifier of class B has high theoretical efficiency of 78.5 percent because-

a.) It is biased almost to saturation

b.)Its quiescent current is low

c.)It’s output is an exact replica of it’s input

d.)It is biased well below cut off56.

The coupling that produces minimum interference with frequency response is-

a.) Direct coupling

b.)Impedance coupling

c.) R C coupling

d.)Transformer coupling57.

In the circuit shown in the given figure Rf provides

a.) Current series feedback

b.)Current shunt feedback

c.) Voltage series feedback

d.)Voltage shunt feedback58.

Mark the correct relation for the junction transistor

59.

Data in the serial form can be converted into parallel form by using –

a.) PISO shift register

b.) SOIP shift register

c.) SIPO shift register

d.) POIS shift register1.The current I in the given network.a) 1A

b) 3Ac) 5Ad) 7A

2.For the Delta‐ Wye transformation in given figure, the value of the resistance R is.a) 1/3 ohmsb) 2/3 ohmsc) 3/2 ohmsd) 3 ohms

3.In the given network, the Thevenin’s equivalent as seen by the load resistance Rl isa) V=10 V, R= 2ohmsb) V=10V, R=3 ohmsc) V=15V, R= 2ohmsd) V=15V, R=3 ohms

4.The current I in a series R‐L circuit with R=10 ohms and L=20mH is given by i=2sin500t A. If v is the voltage across the R‐L combination then ia) lags v by 45 degreeb) is in‐phase with vc) leads v by 45d) lags v by 90

5.In thr given network, the mesh current I and the input impedance seen by the 50 V source, respectively, area) 125/13 A and 11/8 ohmsb) 150/13 A and 13/8 ohmsc) 150/13 A and 11/8 ohmsd) 125/13 A and 13/8 ohms

6.A voltage sourcehaving a source impedance Z = R + jX can deliver maximum Average power to a load impedance Z, whena) Z = R + jXb) Z = Rc) Z = jXd) Z = R –jX

7.In the given circuit, the switch S is closed at t=0. Assuming that there is no initial Charge in the capacitor, the current i(t) for t>0 isa) V/R e^ (‐2t/RC)b) V/R e^ (‐t/RC)c) V/2R e^ (‐2t/RC)d) V/2R e^ (‐t/RC)

8.For the circuit in given figure, if e(t) is a ramp signal, the steady state value of the Output voltage v(t) isa) 0b) LC

c) R/Ld) RC

9.For the series RLC circuit in given figure, if w=1000 rad/sec, then the current I (in Amperes) isa) 2 ∟‐15b) 2 ∟15c) √2∟‐15d) √2∟15

10.The Y‐parameter matrix (mA/V) of the two‐port given network isa) [2 ‐1 ‐1 2]b) [2 1 ‐1 2]c) [1 ‐2 ‐1 2]d) [2 1 1 2]

11.The maximum number of trees of the given graph isa) 16b) 25c) 100d) 125

12.Given figure shows a graph and one of its trees. Corresponding to the tree, the group of branches that CAN NOT constitute a fundamental cut set isa) 1,2,3b) 1,4,6,8,3c) 5,6,8,3d) 4,6,7,3

13.The Y‐parameter matrix of a network is given by Y=[1 1 ‐1 1] A/V. The Z11 parameter of the same network isa) ½ ohmsb) 1/√2 ohmsc) 1 ohmsd) 2 ohms

14.For the given circuit, the switch was kept closed for a long time before opening it at t=0. The voltage v(0+) isa) ‐10 Vb) ‐1 Vc) 0Vd) 10 V

15.The input impedance of a series RLC circuit operating at frequency W=√2w, w being the resonant frequency, isa) R‐j(wL/√2) ohmsb) R+j(wL/√2) ohmsc) R‐j√2wL ohms

d) R‐j√2wL ohms

16.The threshold voltage V is negative fora) an n‐channel enhancement MOSFETb) an n‐channel depletion MOSFETc) an p‐channel depletion MOSFETd) an p‐channel JFET

17.At a given temperature, a semiconductor with intrinsic carrier concentration ni= 10 ^ 16 / m^3 is doped with a donor dopant of concentration Nd = 10 ^ 26 /m^3. Temperature remaining the same, the hole concentration in the doped semiconductor isa) 10 ^ 26 /m^3b) 10 ^ 16 /m^3c) 10 ^ 14 /m^3d) 10 ^ 6 /m^3}

18.At room temperature, the diffusion and drift constants for holes in a P‐type semiconductorwere measured to be Dp = 10 cm^2/s and µp = 1200 cm^2/V‐s, respectively. If the diffusion constant of electrons in an N‐type semiconductor at the same temperature is Dn = 20 cm^2/s, the drift constant for electrons in it isa) µn = 2400 cm^2/V‐sb) µn = 1200 cm^2/V‐sc) µn = 1000 cm^2/V‐sd) µn = 600 cm^2/V‐s

19.A common LED is made up ofa) intrinsic semiconductorb) direct semiconductorc) degenerate semiconductord) indirect semiconductor

20.When operating as a voltage regulator, the breakdown in a Zener diode occurs due to thea) tunneling effectb) avalanche breakdownc) impact ionizationd) excess heating of the junction.

21.If the common base DC current gain of a BJT is 0.98, its common emitter DC current gain isa) 51b) 49c) 1d) 0.02

22.Negative resistance characteristics is exhibited by aa) Zener diodeb) Schottky diode

c) photo dioded) Tunnel diode

23.Let En and Ep, respectively, represent the effective Fermi levels for electrons and holes during current conduction in a semiconductor. For lasing to occur in a P‐N junction of band‐gap energy 1.2 eV, (En ‐ Ep) should bea) greater than 1.2eVb) less than 1.2eVc) equal to 1.1eVd) equal to 0.7eV

24.In a P‐well fabrication process, the substrate isa) N‐type semiconductor and is used to build P‐channel MOSFETb) P‐type semiconductor and is used to build P‐channel MOSFETc) N‐type semiconductor and is used to build N‐channel MOSFETd) P‐type semiconductor and is used to build N‐channel MOSFET

25.In a MOS capacitor with n‐type silicon substrate, the Fermi potential ¢ = ‐0.41 V and the flat‐band voltage Vfb = 0V. The value of the threshold voltage Vt isa) ‐0.82 Vb) ‐0.41 Vc) 0.41 Vd) 0.82Refer given figure for question 26 and 27. Assume D1 and D2 to be ideal diodes.

26.Which one of the following statements is true?a) Both D1 and D2 are ON.b) Both D1 and D2 are OFF.c) D1 is ON and D2 is OFF.d) D2 is ON and D1 is OFF.

27.Values of Vo and I, respectively, area) 2V and 1.1 mAb) 0V and 0 mAc) ‐2V and 0.7 mAd) 4V and 1.3 mA

28.In a BJT CASCODE pair, aa) common emitter follows a common baseb) common base follows a common collectorc) common collector follows a common based) common base follows a common emitter

29.Inside a 741 op‐amp, the last functional block is aa) differential amplifierb) level shifterc) class‐A power amplifierd) class‐AB power amplifier

30.For the MOSFET in the given circuit, the threshold voltage Vt = 0.5V, the process parameter KP = 150 µA/V^2 and W/L = 10. The values of Vd and Id, respectively, area) Vd = 4.5 V and Id = 1 mAb) Vd = 4.5 V and Id = 0.5 mAc) Vd = 4.8 V and Id = 0.4 mAd) Vd = 6 V and Id = 0 mA

31.A negative feedback is applied to an amplifier with the feedback voltage proportional to the output current. This feedback increases thea) input impedance of the amplifierb) output impedance of the amplifierc) distortion in the amplifierd) gain of the amplifier

32.The early effect in a BJT is modeled by the small signal parametera) r0b) r∏c) gmd) β

33.For a given filter order, which one of the following type of filters has the least amount of ripple both in pass‐band and stop‐band?a) Chebyshev type Ib) Besselc) Chebyshev type IId) Elliptic

34.For a practical feedback circuit to have sustained oscillation, the most appropriate value of the loop gain T isa) 1b) ‐1c) ‐1.02d) 1.02

35.Assume the op‐amps in given figure to be ideal. If the input signal vi is a sinusoid of 2V peak‐to‐peak and with zero DC component, the output signal vo is aa) sine waveb) square wavec) pulse traind) triangular wave

36.In a common source amplifier, the mid‐band voltage gain is 40 dB and the upper cutoff frequency is 150kHz. Assuming single pole approximation for the amplifier the unity gain frequency fT isa) 6 MHzb) 15 MHzc) 150 MHz

d) 1.5 GHz

37.An op‐amp is ideal except for finite gain and CMRR. Given the open loop differential gain Ad=2000,CMRR = 1000, the input to the noninverting terminal is 5.002 V and the input to the inverting terminal is 4.999 V, the output voltage of the op‐amp isa) 14 Vb) 24 Vc) ‐6 Vd) ‐8 V

38.The op‐amp in the circuit in given figure has a non‐zero DC offset. The steady state value of the output voltage Vo isa) –RC dvs(t)/ dtb) – (1/RC)|vs(t)dtc) –Vd) +V

39.For the circuit in given figure, if the value of the capacitor C is doubled, the duty‐cycle of the output waveform Voa) increases by a factor of 2b) increases by a factor of 1.44c) remains constantd) decreases by a factor of 1.44

40.Assume the op‐amp in the given circuit to be ideal. The value of the output voltage Vo isa) 3.2 Vib) 4 Vic) 9 Vid) 10 Vi

41.The complement of the Boolean expression F = (X + Yˉ + Z)(Xˉ + Zˉ)(X + Y) isa) XYZ+XZˉ+YˉZb) XˉYZˉ+XZ+XˉYˉc) XˉYZˉ+XZ+YZd) XYZ+XˉYˉ

42.The Boolean function F(A,B,C,D) = ∑(0,6,8,13,14) with don’t care conditions d(A,B,C,D) = ∑(2,4,10) can be simplified toa) F = BˉDˉ+CDˉ+ABCˉb) F = BˉDˉ+CDˉ+ABCˉDc) F = ABˉDˉ+CDˉ+ABCˉd) F = BˉDˉ+CDˉ+ABCD

43.The Boolean function F = AˉDˉ+BˉD can be realized by one of the following figures44. For the multiplexer in given figure, the Boolean expression for the output Y isa) AˉBˉ+BˉCˉ+ACb) ABˉ+BˉCˉ+ACˉc) ABˉ+BˉC+AC

d) AˉBˉ+BˉC+AˉC

45. Which one of the following is TRUE?a) Both latch and flip‐flop are edge triggered.b) A latch is level triggered and a flip‐flop is edge triggered.c) A latch is edge triggered and a flip‐flop is level triggered.d) Both latch and flip‐flop are level triggered.

46. In a schottky TTL gate, the Schottky diodea) increases the propagation delayb) increases the power consumptionc) prevents saturation of the output transistord) keeps the transistor in cutoff region

47. For which one of the following ultraviolet light is used to erase the stored contentsa) PROMb) EPROMc) EEPROMd) PLA

48. Which one of the following is NOT a synchronous countera) Johnson counterb) Ring counterc) Ripple counterd) Up‐down counter

49. In 8085 microprocessor, the accumulator is aa) 4 bit registerb) 8 bit registerc) 16 bit registerd) 32 bit register

50. In the register indirect addressing mode of 8085 microprocessor, data is stored a) at the address contained in the register pairb) in the register pairc) in the accumulatord) in a fixed location of the memory

51. The output w[n] of the system shown in given figure isa) x[n]b) x[n‐1]c) x[n] – x[n‐1]d) 0.5(x[n‐1] + x[n])

52. Which one of the following is a periodic signala) x(t) = 2 e^j(t+(π/4))b) x[n] = u[n] + u[‐n]c) x[n] = ∑{∂[n‐4k]‐∂[n‐1‐4k]} where k = ‐∞to ∞

d) x(t) = e^ (‐1+j)t

53. If the input‐output relation of a system is y(t) = ∫x(t) dt where t = ‐∞ to 2ta) linear, time‐invariant and unstableb) linear, non‐causal and unstablec) linear, causal and time invariantd) non‐causal, time invariant and unstable

54. Which one of the can be the magnitude of the transfer function | H(jw) | of a causal system

55. Consider the function H(jw) = H1(w) + jH2(w), where H1(w) is an odd function and H2(w) is an even function. The inverse Fourier transform of H(jw) isa) a real and odd function b) a complex functionc) a purely imaginary functiond) a purely imaginary and odd function56. The laplace transform of given signal isa) –A((1‐e^cs)/s)b) A((1‐e^cs)/s)c) A((1‐e^‐cs)/s)d) –A((1‐e^‐cs)/s)57. If X(z) is the z‐transform of x[n] = (1/2)^ |n|, the ROC of X(z) isa) |z| > 2b) |z| < 2c) 0.5<|z|<2

d) the entire z‐plane58. In a linear phase system, τg the group delay and τp the phase delay area) constant and equal to each otherb) τg is a constant and τp is proportional to wc) a constant and τg is proportional to wd) τg is proportional to w and τp is proportional to w

59. A signal m(t), band‐limited to a maximum frequency of 20 kHz is sampled at a frequency fs kHz to generate s(t). An ideal low pass filter having cut‐off frequency 37 kHz is used to reconstruct m(t) from s(t). The maximum value of fs required to reconstruct m(t) without distortion isa) 20 kHzb) 40kHzc) 57 kHzd) 77 kHz

60. If the signal x(t) shown in given figure is fed to an LTI system having impulse response h(t) as shown in given figure, the value of the DC component present in the output y(t) isa) 1b) 2c) 3d) 4

61. The characteristic equation of an LTI system is given as s^3 + Ks^2 + 5s + 10. When the system is marginally stable, the value of K and the sustained oscillation frequency w, respectively, area) 2 and 5b) 0.5 and √5c) 0.5 and 5d) 2 and √5

62. The time required for the response of a linear time‐variant system to reach half the final value for the first time isa) delay timeb) peak timec) rise timed) decay time

63. The signal flow graph of the given network is

64. Let c(t) be the unit step response of a system with transfer function K(s+a)/(s+K). If c(0+)=2 and c(∞)=10, then the values of a and K, respectively, area) 2 and 10b) ‐2 and 10c) 10 and 2d) 2 and ‐10

65. The loop transfer function of an LTI system is G(s)H(s)= K(s+1)(s+5) / s(s+2)(s+3). For K>0, the point on the real axis that DOES NOT belong to the root locus of the system isa) ‐0.5b) ‐2.5c) ‐3.5d) ‐5.5

66. The state space equation of the circuit shown in given figure for x1=v0, x2=I is

67. The open loop gain of a unity feedback system is G(s)=wn^2 / s(s+2wn). The unit step response c(t)of the system is

69. The angles of the asymptotes of the root loci of the equation s^3 + 5s^2 + (K+2)s + K = 0, for0<=K<∞, area) 0 and 270b) 0 and 180c) 90 and 270d) 90 and 180

70. The bode plot corresponding to a proportional derivative controller is the one shown in given figure

71. In frequency modulation, the instantaneousa) amplitude of the carrier signal is varied with the instantaneous amplitude of the message signalb) amplitude of the carrier signal is varied with the instantaneous frequency of the message signalc) frequency of the carrier signal is varied with the instantaneous amplitude of the message signald) frequency of the carrier signal is varied with the instantaneous frequency of the message signal

72. If X is a zero mean Gaussian random variable, then P{X<=0} isa) 0b) 0.25c) 0.5d) 1

73. If a single‐tone amplitude modulated signal at a modulation depth of 100% transmits a total power of 15W, the power in the carrier component isa) 5Wb) 10Wc) 12Wd) 15W

74. In a superheterodyne receiver, rejection of the image signal can be achieved by using aa) higher local oscillatorn frequencyb) crystal oscillatorc) narrow band IF filterd) narrow band filter at RF stage

75. The number of bbits per sample of a PCM system depends upon thea) sampler typeb) quantizer typec) number of levels of the quantizerd) sampling rate

76. Which one of the following is used for the detection of AM‐DSB‐SC signala) Ratio detectorb) Foster‐Seeley discriminatorc) Product demodulatord) Balanced‐slpoe detector

77. Which one of the following signal pairs can represent a BPSK signala) A cos2πfct, A sinπfctb) A cos2πfct, ‐ A sinπfctc) ‐ A cos2πfct, A sinπfctd) A sin2πfct, A cosπfct

78. Which one of the following can be used for the detection of the noncoherent BPSK signala) matched filterb) phase‐locked loopc) envelope detectord) product demodulator

79. Bits of duration Tb are to be transmitted using a BPSK modulation with a carrier of frequency Fc Hz. The power spectral density of the transmitted signal has the first null at the normalized frequencya) |F – Fc|Tb = 0b) |F – Fc|Tb = 1c) |F – Fc|Tb = 2d) |F – Fc|Tb = 4

80. The probability of bit error of a BPSK modulation scheme, with transmitted signal energy per bit Eb, in an additive white Gaussian noise channel having one‐sided power spectral density N0, isa) (1/2) erfc(Eb/2N0)b) (1/2) erfc√(Eb/2N0)c) (1/2) erfc(Eb/N0)d) (1/2) erfc√ (Eb/N0)

81. For a given transmitted pulse p(t), 0<=t<=T, the impulse response of a filter matched to the received signal isa) –p(t‐T), 0<=t<=Tb) –p(T‐t), 0<=t<=Tc) p(t‐T), 0<=t<=Td) p(T‐t), 0<=t<=T

82. The multiple access communication scheme in which each user is allocated the full available channel spectrum for a specified duration of time is known asa) CDMAb) FDMAc) TDMAd) MC‐CDMA

83. GSM system uses TDMA witha) 32 users per channelb) 16 users per channelc) 8 users per channeld) 4 users per channel

84. If Rx(τ) is the auto‐correlation function of a zero‐mean wide‐sense stationary random process X, then which one of the following is NOT true?a) Rx(τ) = Rx(‐τ)b) Rx(τ) = ‐Rx(‐τ)c) σx^2 = Rx(0)d) |Rx(τ)| <=Rx(0)

85. If E denotes the expectation operator, then E[X‐EX]^3 of a random variable X isa) EX^3 – E^3Xb) EX^3 + 2E^3X – 3EX Ex^2c) 3EX^3 – E^3Xd) 2EX^3 + E^3X – 3EX EX^2

86. A discrete memoryless source produces symbols m1,m2,m3 and m4 with probabilities 1/2, 1/4 , 1/8 and 1/8, respectively. The entropy of the source isa) ¼b) 1c) 7/4d) 2

87. A channel has a signal‐to‐noise ratio of 63 and bandwidth of 1200 Hz. The maximum data rate that can be sent through the channel with arbitrary low probability of error isa) 600 bpsb) 1200 bpsc) 4800 bpsd) 7200 bps

88. For the vectors A = X ax + Y ay and B = Z az, del . (A X B) isa) 0b) 1c) XZd) YZ

89. Which one of the following relations represents Strokes’ theorem (symbols have their usual meaning)?a) ∫s del X A.ds = 0b) ∫L A.dl = ∫s del X A.dsc) ∫s A X dS = ‐∫v (del X A)dvd) ∫v del.Adv = ∫s A.ds

90. Which one of the following relations is not correct (symbols have their usual meaning)?a) del X E = ‐ ∂B/∂tb) del X H = J + ∂E/∂tc) del.D = ρvd) del.B = 0

91. The electric field component of a uniform plane wave propagating in a lossless magnetic dielectric medium is given by E(t,z)=ax 5cos(10^9 t – 20/3 z)V/m. If η0 represents the intrinsic impedance of the free space, the corresponding magnetic field component is given bya) H(t,z)= ay 5/2 η0 cos(10^9t – 20/3 z)A/mb) H(t,z)= ay 10/ η0 cos(10^9t – 20/3 z)A/mc) H(t,z)= az 5/2 η0 cos(10^9t – 20/3 z)A/md) H(t,z)= az 10/ η0 cos(10^9t – 20/3 z)A/m

92. The skin depth of a non‐magnetic conducting material at 100 MHz is 0.15 mm. The distance which a plane wave of frequency 10 GHz travels in this material before its amplitude reduces by a factor of e^‐1 isa) 0.0015 mmb) 0.015 mmc) 0.15 mmd) 1.5 mm

93. A lossless transmission line has a characteristic impedance of 100 ohms and an inductance per unit length of 1 μH/m. If the line is operated at 1 GHz, the propagation constant β isa) 2π rad/mb) 20π/3 rad/mc) 20π rad/md) 2π *10^5 rad/m

94. When a load resistance Rl is connected to a lossless transmission line of characteristic impedance 75 ohms, it results in a VSWR of 2. The load resistance isa) 100 ohmsb) 75√2 ohmsc) 120 ohmsd) 150 ohms

95. A two‐port network characterized by the S‐parameter matrix, [S] = [0.3 L0 0.9 L90 0.9 L90 0.2 L0] Isa) both reciprocal and losslessb) reciprocal, but not losslessc) lossless, but not reciprocald) neither reciprocal nor lossless

96. A lossless air filled rectangular waveguide has internal dimensions of a cm * b cm. If a=2b and the cutoff frequency of the TE02 mode is 12 GHz, the cutoff frequency of the dominant mode isa) 1 GHzb) 3 GHzc) 6 GHzd) 9 GHz

97. A Hertzian dipole antenna is placed at the origin of a coordinate system and it is oriented along z‐axis. In which one of the following planes the radiation pattern of the antenna has a circular shape?a) x=0b) y=0c) z=0d) ø=45

98. Which one of the following statements is not true?

a) Antenna losses are taken into account in calculating its power gainb) For an antenna which does not dissipate any power, the directive gain and the power gain are equal c) Directivity of an antenna is the maximum value of its directive gaind) The directive gain of a Hertzian dipole is same in all direction

99. The directivity of a half dipole antenna isa) 1.0b) 1.5c) 1.64d) 2

100. Which one of the following is not true for a step index optical fibre?a) It can support multiple modesb) HE11 mode is its lowest order modec) The refractive index of the cladding is higher than that of the cored) At a given wavelength, single mode operation is possible by proper choice of core diameter, core and cladding refractive indices.