BEL Technical Questions with answers

1. The gray code equivalent of binary 1100 is

a. 1011 b. 1101 c. 1010-and d. 1100



2. A Multiplexer has

a. Multiple inputs and single output

b. Single input and Multiple outputs

c. Multiple inputs and Multiple outputs-ans

d. Multiple inputs for Storage of Data



3. A binary half adder

a. Adds two binary digits and produces their sum and carry-ans

b. Adds half the sum to the carry

c. Adds two binary digits and carry from previous addition

d. Adds two binary digits at half the speed



4. An index register in a computer is for

a. Arithmetic and logic functions

b. Storage of results

c. Modifying the address-ans

d. Counting the no of programmes



5. An example of volatile memory is

a. RAM-ans b. ROM c. EPROM d. Magnetic tape



6. Barrier voltage in a P-N junction is caused by

a. Thermally generated electrons and holes

b. Diffusion of majority carriers across the junction-ans

c. Migration of minority carriers across the junction

d. Flow of drift current



7. The temperature coefficient of an intrinsic semiconductor is

a. Positive b. Negative-ans c. Zero d. Like metals



8. A silicon transistor has a leakage current 1cbo = 1 ma. If the temp. rises by 50o C the leakage current will be

a. 30 ma b. 32ma-ans c. 50ma d. no change



9. The noise figure of an ideal amplifier in decibel is

a. 0.5 b. 0-ans c. 1 d. 10



10. The rise time of an amplifier is 200 nsec. Its bandwidth is

a. 70MHz b. 140MHz c. 100MHz d. 1.75Mhz-ans



11. MOSFET operates in

a. Depletion mode only

b. Enhancement mode only

c. Depletion and enhancement mode-ans

d. None of these of the above



12. A device which behaves like SCRs is

a. UJT b. Triac-ans c. MOSFET d. SRD



13. A plate modulated class C RF amplifier produces 100 KW of radiated power at 100 % modulation. The modulating audio amplifier supplies approximately

a. 25KW b. 33KW-ans c. 50KW d. 66KW



14. A 100 MHz FM carrier, modulated by a 5 KHz sine wave deviates by 50 KHz If the frequency of the modulating sine wave is doubled, the deviation will

a. Double b. Half c. Quadruple d. Have no change-ans



15. Noise generated by a resistor is dependent on

a. Its Value

b. Its temperature

c. Both value and temp-ans

d. None of these



16. A 32 channel 8 bit PCM system samples at 8 KHz rate. The overall bit rate in kilobits per second will be

a. 2048-ans b. 2000 c. 1920 d. 64



17. Stub matching eliminates standing wave on

a. Load side of the stub

b. Source side of the stub

c. Both sides-ans

d. On the stub



18. A half wave folded dipole has a radiation resistance of

a. 72 W b.50W c. 144W d. 288W-ans



19. Top loading is used in antennas for

a. Decrease in impedance

b. Increase in bandwidth

c. Increase in effective height-ans

d. Decease the height



20. The term critical frequency in Ionospheric propagation is

a. Lowest frequency reflected by Ionosphere

b. Highest frequency reflected by the Ionosphere at vertical incidence-ans

c. Lowest frequency reflected by the Ionosphere at vertical incidence

d. Lowest communication frequency possible



21. The cathode ray oscilloscope can be used to measure

a. Frequency b. Time interval c. Voltage d. All the above-as



22. A wein bridge is used for measurement of

a. Resistance b. Capacitance c. Inductance d. Audio frequency-ans



23. The frame rate per second used in India TV is

a. 60 b. 50 c. 25-ans d. 30



24. VHF signals are propagated

a. Via the ionosphere

b. Along the ground-ans

c. Through the troposphere

d. By reflection in ionosphere



25. The impedance of a 3 element yagi antenna is around

a. 75W b. 300W-ans c. 50W d. 100W



26. A PIN diode is microwave

a. Oscillator b. Mixer c. Detector d. Switch-ans



27. A transmission line of VSWR 2 has a reflection coefficient

a. 0.25 b. 0.5 c. 75-ans d. 0



28. Microwave repeaters are typically

a. 25 b. 50-ans c. 75 d. 100 Kms apart



29. To overcome fading in a ship-to-ship communication system we can efficiently use

a. Broadband Antenna

b. Directional Antenna

c. Space Diversity

d. Frequency Diversity-ans



30. Frequency in the UHF range is propagate by waves of

a. Ground b. sky c. Space-ans d. Surface



31. A duplexer is used to

a. Receive two signals in one antenna

b. Prevent interference between two antenna

c. Mix two signals to the same antenna

d. Allow one antenna for both transmission and reception-ans



32. Strapping is used in a magnetron to

a. Prevent mode jumping-ans

b. Reduce frequency drift

c. Ensure proper bunching

d. Dissipate heat



33. A rectangular waveguide behaves like a filter of

a. Band pass b. High pass-ans c. Low pass d. Band stop



34. The signal propagation time in milliseconds for a geosynchronous satellite is

a. 540 b. 270 c. 135-ans d. 100



35. The silicon solar cell is a

a. Photo conductive

b. Photo emissive

c. Photo voltaic-ans

d. Photo resistive



36. For the national TV and ratio network, INSAT-IB uses

a. 400MHz b. 2.5GHz c. 2.5 and 5GHz d. 4 and 6 GHz-ans



37. A typical fibre-optic detector is

a. Step recovery diode

b. Light emitting diode

c. Avalanche photo diode-ans

d. Field effect transistor



38. A modem is a device used for

a. Digitizing voice data

b. Transmission of data on lines

c. Modulating and demodulating signals sent on a line-ans

d. Suppressing noise interference



39. The most effective anti-jamming technique is

a. Frequency hopping-ans

b. Spread Spectrum

c. Frequency synthesis

d. Burst transmission



40. Mono-mode is a term used in

a. Fibre-optics-ans

b. Radar

c. Satellite communication

d. Magnetics



41. Monopulse technique is used in

a. Radar-ans

b. Radio relay

c. Data communication

d. Fibre-optics



42. HDLC is a term for

a. Data communication protocol-ans

b. Synchronizing pulses

c. Gain control in receivers

d. Error checking



43. A gateway

a. Is a place where radars are connected

b. Permits dissimilar networks to communicate-ans

c. Bifurcates the RF path of a transmitter

d. Is a feeder cable



44. Ethernet is a name of

a. Medium of computer communication

b. Network for computer communication-ans

c. Procedures for computer communication network

d. Software for computer communication



45. If several stations in a network want to use a single channel without interfering with one another,

the technique used is called

a. Carrier sense

b. Phantom-freeze

c. Packet switching

d. Multiplexing-ans



46. In a monolithic IC, resistors are formed from

a. Ceramic materials

b. Copper

c. P-type semiconductor-ans

d. Aluminium deposition



47. ICs made by sputtering of materials on a ceramic substrate are called

a. Monolithic b. Hybrid c. Thick film d. Thin film-ans



48. Two coils (inductors) connected in series have a combined inductance of 15mH. When terminals of one of the coils are reversed and connected to the other, the combined inductance is measured to be 9mH. What is the value of mutual inductance

a. 1.5mH b.3mH c.6mH d.12mH



49. If a parallel LC circuit is excited at frequency less than its resonant frequency, the nature of its effective impedance is

a. Resistive b. Inductive c. Capacitive d. None of these of these



50. The wave length of 1 Giga hertz frequency signal is

a. 10cm b. 30cm c. 3cm d. 1cm



51. Which of the following microwave tubes can be considered as broad band devices

a. Magnetrons

b. Klystrons

c. Reflex klystrons

d. Traveling wave tubes[TWT]



52. Which family of the following integrated circuits has the highest speed

a. DTL b. ECL c. TTL d.CMOS



53. The most important feature of CMOS family of ICs is

a. High speed

b. Small size

c. Low power consumption

d. Low input impedance



54. What is the resolution of 8 bit A/D converter if its full scale voltage is 10v

a. 0.02v b. 0.01 c. 0.039v d. 0.078v



55. What value of resistance is to be used in LSB of 4 bit weighted ladder D/A converter if MSB has 10 kW resistor

a. 160k b. 80k c. 240k d. 100k



56. The pulse width of a radar transmitter is 0.6m sec. and the pulse repetition rate is 700 Hz. The average power measured is 420 watts. What is the peak power

a. 100KW b. 420KW c. 1MW d. None of these



57. The device used for isolating the transmitter and receiver in a radar system is called

a. Diplexer

b. Duplexer

c. Directional coupler

d. None of these



58. “Baud” is

a. Total No. of bits/sec in each character

b. Reciprocal of shortest signal element in a character

c. Duration of a character in data transmission

d. None of these



59. The advantage of Totem pole output stage in TTL ICs is

a. Low output impedance

b. Can sink more current

c. Oscillations avoided

d. None of these



60. The capacitance value of a varactor is controlled by

a. A reverse voltage applied to it

b. A series resistance

c. Varying its supply voltage

d. Current through the device

Answers

b50. b51. d52. b53. c54. c55. b56. c57. b58. b59. a60. a



61. Electron volt is equivalent to

a. 3.8 * 10-20 erg

b. 1.602 * 10-12 erg

c. 1.602 * 10-18 erg

d. 1.602 * 10-16 erg



62. The kinetic energy of photo electrons emitted by a photo sensitive surface depends on

a. Intensity of the incident radiation

b. Wavelength of the incident radiation

c. Angle of incident of radiation

d. Surface conditions of the surface



63. Flux is expressed in radio-metric system in

a. Lumens

b. Photons

c. Watts

d. Candles



64. In a three-phase bridge rectifier circuit, the ripple frequency is

a. Same as line frequency

b. Twice the line frequency

c. Thrice the line frequency

d. Six times the line frequency



65. Energy stored in a capacitor as a function of voltage is given by

a. CV2

b. 1V2/2C

c. ½ CV2

d. 1V/2C

66. The operational amplifier used in analog computers have usually open loop flat gain approximately upto

a. 1MHz b. 100MHz c. 10MHz d. 0.1MHz



67. An oscillator of 350 MHz is fed with a pulse of rise time 2 n sec. The rise time of the displayed waveform is approximately

a. 1 n sec b. 2.2 n sec c. 2.0 n sec d. 1.7 n sec



68. A radar transmits a peak power of 100 KW with pulse width of 1 m sec and a pulse repetition rate of 100 KHz. The average output power of the radar is

a. 100KW b.10KW c. 1000KW d. 50KW



69. The incremental inductance in a coil is due to

a. Saturation

b. Superimposed DC

c. Mutual inductance

d. Change of frequency



70. Microwave tube based on velocity modulation principle is

a. Klystron

b. Magnetron

c. Light house tube

d. Traveling wave tube



Answers

61. b62. b63. a64. b65. c66. d67. c68. b69. d70. a71. a72. a73. b74. a75. b76. a77. b78. a79. a80. b

71. Noise output from the receiver decreases uniformly with noise side band frequency for

a. Frequency modulation

b. Amplitude modulation

c. Pulse amplitude modulation

d. None of these



72. In amplitude modulation the maximum permissible modulation index is

a. Unity b. 100 c. infinity d. None of these



73. In frequency modulation the maximum permissible modulation index is

a. Unity b. 50 c.1000 d. no limit



74. In FM transmission and reception, the pre-emphasis and de-emphasis are used to improve the

a. Signal to noise ratio

b. Frequency response of the receiver

c. Frequency response of the transmitter

d. The sensitivity of the transmitter



75. De-emphasis network uses the combination of

a. R-L b. R-C c. R-L-C d. Transformer



76. The usage of micro sec for defining emphasis is a standard practice but this micro sec definition means

a. 3 dB point of the network means

b. mid point of the network response

c. roll off the network response

d. the stop band ripple of the network response



77. Delayed AGC is applied

a. For all singal strength

b. For singal strength exceeding a specified limit

c. For low singal strength

d. For FM receiver



78. Selectivity means

a. Bandwidth

b. Gain

c. Modulation index

d. None of these



79. Narrow bandwidth broadcast reduces

a. The quality and noise

b. Quality alone

c. Noise alone

d. Quality and intelligibility



80. Squelch means keeping the receiver

a. ON in the absence of carrier

b. OFF in the absence of carrier

c. To remove AGC

d. Increase the AGC



81. Let Z be the series impedance and Y be the shunt admittance of the transmission line, then the characteristic impedance

a. ÖZY b.ÖY/Z c. ÖZ/Y d.All the above

82. Noise figure of an amplifier is defined as

a. Input SNR output SNR

b. Input SNR / output SNR

c. Output SNR / input SNR

d. Input SNR / gain



83. A broadcast radio transmitter radiates 10 KW power when modulation is 60%. Its carrier power will be

a. 8.47KW b.8.92KW c. 8.31KW d.10.00KW



84. In AM transmission antenna current is 8 Ampere at zero modulation indexes but increased to 8.93 Ampere when modulated on single sine wave. Then the % of modulation is approximately

a. 70.1% b. 80.1% c. 65.1% d. 10.0%



85. In AM transmission antenna current is 8 Ampere at zero modulation index. At 80% modulation index the antenna current will be

a. 10.00A b. 8.72A c. 9.19A d. 9.79A



86. If two sine waves are amplitude modulated with modulation index m1 and m2, the effective modulation index is

a. Ö m12/m22

b. Ö m1 m2

c. Ö m12+m22

d. Ö m22/m12



87. If it is transmitted current and Ic is transmitter current at zero modulation index and the transmitted current at modulation index of m will

a. It = Ic Ö[1+m]

b. It = Ic Ö[1+m2]

c. It = Ic Ö[1+m/22]

d. It = IcÖ1+m2



88. If Rr is the radiation resistance and Rd is the lumped resistance, then the antenna efficiency is given

as –

a. (Rr - Rd) / (Rr + Rd)

b. (Rr + Rd) / (Rr – Rd)

c. Rr / (Rr + Rd)

d. Rd / (Rr + Rd)



89. In end fire array, the current

a. Magnitude and phase in each element is the same

b. Magnitude is the same but phase is different in each element

c. Magnitude is different but no phase difference in each element

d. Magnitude and phase are different in each element



90. In a board side array, the current

a. Magnitude and phase in each element is the same

b. Magnitude is the same but phase is different

c. Magnitude is different but no phase difference in each element

d. Magnitude and phase are different in each element



91. Beam width of the 2 metre paraboloid reflector at 6 GHz is

a. 4.5o

b. 9.25o

c. 3.5o

d. 7.75o



92. The cut of wave length for TE m, n mode is in a wave guide of dimension a*b is

a. 2/Ö(m/a)2 +(n/b)2

b. 2Ö [m/a]2 + [n/b]2

c. Ö(m/a)2 + (n/b)2 /2

d. Ö [m/a]2 + [n/b]2



93. For the standard rectangular waveguide dimension of 4*2 cm the off wavelength for TM11 mode is approximately

a. 1.788cm b. 3.576cm c. 1.682cm d. 2.546cm



94. In IMPATT diode, the voltage and current are

a. In phase

b. Out off phase by 90o

c. Out off phase by 180o

d. None of these of the above



95. Which of the following statement is true

a. Tunnel diode & IMPATT diode are negative resistance devices

b. Tunnel diode is positive resistance device and the IMPATT diode is negative resistance device

c. Tunnel diode is negative resistance device and the IMPATT diode is positive resistance device

d. None of these of the above



96. In a SSB modulation system with 100% modulation index the power saving will be

a. 5/6 of carrier power

b. 2/8 of carrier power

c. 5/12 of the carrier power

d. ½ of the carrier power



97. In SSB modulation the modulation index is increased from 0.5 to 1.0, then the power will be increased by

a. 2 times b. 4 times c. 16 times d. 32 times



98. 900 rpm is equal to

a. 94.2 rad/sec

b. 47.1 rad/sec

c. 188.4 rad/sec

d. 16.72 rad/sec



99. Darlington pair is used to

a. Increase the voltage gain

b. Increase the current gain

c. Decrease voltage gain

d. Decrease current gain



100. The transfer function of the system shown is

a. G(s) / {1 + H(s)}

b. G(s) H(s) / {1 + G(s) H(s)}

c. G(s) / {1 + G(s) H(s)} d. G(s) / G(s) H(s)-ans

Answers

81. c82. b83. a84. a85. c86. c87. c88. c89. b90. a91. c92. a93. b94. c95. a96. a97. b98. b99. b100. c

BEL Technical and Electronics Paper with Answers

(Technical-Electronics-IInd)

1. Resistivity of silicon in ohms cm. is approx. equal to

a. 50 b. 1012 c. 230k d. 10-6



2. Rsistivity ofGermanium in ohms cm. is approx. equal to

a. 50 b. 10-12 c. 50k d. 10-6



3. The number of free electrons/cubic cm intrinsic Germanium at room temperature is approx. equal to

a. 1.5*1010 b. 2.5*1013 c. 1000 d. 5*106



4. The number of free electrons/cubic cm of intrinsic silicon at room temperature is approx. equal to

a. 1.5*1010 b. 2.5*1013 c. 10000 d. 5*106



5. The forbidden energy gap for silicon is

a. 1.1eV b. 067eV c. 0.97eV d. 1.7eV



6. The forbidden energy gap for Germanium is

a. 1.1eV b. 067eV c. 0.97eV d. 1.7eV



7. N type material is formed by the addition of the following (penta valent )atom in n to semiconductor material

a. Antimony

b. Arsenic

c. Phosphorous

d. Any of the above



8. P type material is formed by the addition of the following [Trivalent] atom tn to semiconductor material

a. Boron b. Gallium c. Indium d. Any of the above



9. Impurity atoms that produces N type material by its addition in semiconductor is called

a. Donar b. Acceptor c. Conductor d. Insulator



10. Impurity atoms that produces P type material by its addition in semiconductor is called

a. Donar b. Acceptor c. Conductor d. Insulator



11. Dynamic resistance of a diode Rd is if voltage changes is DVd and the current change is D Id

a. D Vd / D Id

b. D Id / D Vd

c. 1 / DVd

d. 1 / D Id



12. Point contact diodes are preferred at very high frequency, because of its low junction

a. Capacitance and inductance

b. Inductance

c. Capacitance



13. Identify the circuit given below

a. AND gate

b. OR gate

c. Rectifier

d. NOR gate



14. Identify the circuit given below

a. AND gate

b. OR gate

c. Rectifier

d. NOR gate



15. DC value of a Half wave rectifier with Em as the peak value of the input is

a. 0.318Em

b. 0.418Em

c. 0.518Em

d. 0.618Em



16. Change in Zener voltage of 10V at 100o C if temperature co-efficient is 0.072%o C as

a. 0.54 V b. 0.74 V c. 0.64 V d. 0.14 V



17. If Tc is th e% temperature co of / oC and Vz as zener voltage and T as change in temperature then

the change in zener voltage is



c. 100. Vz. Tc DT

d. None of these of the above



18. PIV for a full wave rectifier, if Em is the peak voltage is

a. Em b. 1.5Em c. 0.636Em d. 2Em



19. Schottky Barrier diodes becomes important at

a. DC level operation

b. Low frequency operation

c. High frequency operation

d. None of these



20. Clamping network is the one that will clamp the signal to a

a. Different peak value

b. Different DC level

c. Different polarity level

d. Different RMS level

Answers

1. c2. a3. a4. b5. a6. b7. d8. d9. a10. b11. a12. c13. b14. a15. a16. a17. a18. d19. c20



21. Clipping network is the one that will clip a portion of the

a. Input signal without distorting the remaining portion

b. Input signal with distorting the remaining portion

c. Any of the above

d. None of these



22. Transition capacitance Ct of a Varicap diode with Knee voltage Vt, reverse voltage Vr and K, the

constant based on semiconductor material and the construction technique & N dependent on type of

junction is given by

a. 1 / K (Vt + Vr)N/2

b. 1 / K (Vt + Vr)N

c. K / (Vt + Vr)N

d. K / (Vt + Vr)1/N



23. Ct = K / (Vt + Vr)N where Vt Knee voltage, Vr reverse voltage, K manufacturing dependent constant and N dependent on type of junction, for alloy junction the value of N is

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



24. Ct = K / (Vt + Vr)N where Vt Knee voltage, Vr reverse voltage, K manufacturing dependent constant and N dependent on type of junction, for diffused junction the value of N is

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



25. In JFET, the drain current Id is given by (Idss drain – source saturation current Vgs – Gate – source voltage, Vp the pinch off voltage)

a. Idss[1 – Vp/Vgs]

b. Idss(1 – Vgs/Vp)2

c. Idss[1 – Vgs/Vp)

d. Idss(1 – Vgs/Vp)3/2



26. The shadow mask in colour tube is used to

a. Reduce X-Ray emission

b. Ensure each beam hits its own dots

c. Increase screen brightness

d. Provide degaussing for the screen



27. Indicate which of the following signal is not transmitted in colour TV

a. Y b. Q c. R d. I



28. Another name for horizontal retrace in TV receiver is the

a. Ringing b. Burst c. Damper d. Fly back



29. Another name for the colour sync in the colour TV system

a. Ringing b. Burst c. Damper d. Fly back



30. The HV anode supply for a picture tube of a TV receiver is generated in the

a. Mains transformer

b. Vertical output stage

c. Horizontal output stage

d. Horizontal oscillator



31. The output of vertical amplifier is

a. Direct current

b. Amplified vertical sync pulse

c. A saw tooth voltage

d. A saw tooth current



32. In a transistor if Alpha = 0.98, current gain is equal to

a. 29 b. 59 c. 69 d. 49



33. The active region in the common emitter configuration means

a. Both collector and emitter junction is reverse biased

b. The collector junction is forward biased and emitter junction

c. The collector junction is reverse biased and emitter junction is forwared biased

d. Both collector & emitter junction are forward biased



34. The saturation region in the common emitter configuration means that

a. Both collector & emitter junction are reverse biased

b. The collector junction is forward biased and emitter junction

c. The collector junction is reverse biased and emitter junction is forwared biased

d. Both collector & emitter junction are forward biased



35. The % of Red, Green & Blue in 100% White Y is given by

a. 30%, 59%, 11%

b. 50%, 30%, 11%

c. 30%, 11%, 50%

d. 33.3%, 33.5%, 38.3%



36. Equalizing pulse width, if H is the Horizontal sync rate

a. 0.64 H b. 0.07 H c. 0.04 H d. 0.16 H



37. In a simple RC network the bandwidth is equal to

a. 1/2 p RC

b. RC / 2

c. 2 C / p R

d. 2 p / RC



38. The time constant of a RC network is given by

a. RC b. C/R c. R/C d. None of these



39. First zero crossing of pulse frequency spectrum occurs at if d is the pulse width, T is the pulse repetition rate

a. 1/d b. d/T c. T/d d. T



40. The distortion less output characteristic of a network means

a. Constant amplitude and linear phase shift over frequency

b. Linear phase shift and amplitude need not be constant

c. Any amplitude and phase

d. None of these



41. Single sideband means suppressed

a. Carrier

b. Carrier and one side band

c. One side band

d. None of these



42. In an amplitude modulated signal, lower side band frequency is equal to (if the carrier frequency is fc and modulation frequency is fm)

a. fm + fc b. fc – fm c. fm r fc d. fc / fm



43. Modulation index of the frequency modulation depends on

a. Amplitude & frequency of the modulation signal

b. Frequency and amplitude of carrier signal

c. Carrier frequency

d. None of these



44. The BW of the narrow band FM if modulating frequency is fm

a. 3 r fm b. 2 r fm c. 2.5 r fm d. 10 r fm



45. Reactance tube modulator is known for

a. FM b. AM c. PPM d. PAM



46. Bandwidth and rise time product is

a. 0.35 b. 0.45 c. 0.30 d. 0.49



47. Energy gap, Lg, for Germanium at room temp [300o K] is

a. 0.72eV b. 1.1eV c. 1.53eV d. 0.2eV



48. Volt equivalent of temperature VT, at 116o K is

a. 0.11V b. 0.01V c. 1.16V d. 0.1V



49. Reverse saturation current of a Ge.diode is in the range of

a. mA b. uA c. nA d. pA



50. Cut-in voltage V for silicon is approximately

a. 0.2V b. 0.6V c. 0.9V d. 1.1V

Answers

b21. a22. c23. c24. a25. b26. b27. c28. d29. b30. c31. d32. d33. c34. d35. a36. c37. a38. d39. a40. a41. b42. b43. a44. b45. b46. a47. a48. b49. b50.

51. Every 10o C rise in temp. the reverse saturation current

a. Doubles

b. Halves

c. Triples

d. No change



52. Hall effect with reference to Metal or Semiconductor carrying a current I is placed in a transversemagnetic field B, an electric field E is induced in

a. Parallel to B

b. Perpendicular to I

c. Perpendicular to both B & I

d. Perpendicular to B



53. 1 eV (electron volt) is equal to:

a. 1.9 r 10-20 J

b. 1.6 r 10-19 J

c. 1.6 r 10-20 J

d. 1.16 r 10-19 J



54. Donar impurity is having a valency of:

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



55. Acceptor impurity is having a valency of

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



56. Electron volt arises from the fact that if any electron falls through a potential of 1 volt, its kinetic energy will

a. Decrease, & potential energy will increase

b. Increase & potential energy decrease

c. Be unaltered & potential energy decreases

d. Increase & potential energy increase



57. Hole is created in a semiconductor material if one of following impurities are added

a. Antimony

b. Arsenic

c. Indium

d. Phosphorus



58. Excess electron is created by

a. Boran

b. Gallium

c. Indium

d. Arsenic



59. A snubber circuit is used across the SCR to protect against

a. The di/dt of the anode current

b. The dv/dt turn on

c. L.di/dt of load inductance

d. None of these



60. Germanium has the valency of

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



61. Silicon has the valency of

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



62. Hole acts as a free charge carrier of polarity

a. Negative

b. Positive

c. Neutral

d. None of these



63. Burst signal in NTSC system is 8 cycles of the frequency of

a. Colour sub carrier

b. Picture carrier

c. Sound carrier

d. None of these



64. Colour sub carrier reference burst is superimposed on the

a. Back porch of the each horizontal sync pulse

b. Front porch of the each horizontal sync pulse

c. Front porch of the each vertical sync pulse

d. Back porch of the each vertical sync pulse



65. The law of mass action with reference to semiconductor technology states that the product of free negative & positive concentration is a constant and

a. Independent of amount of donor and acceptor doping

b. Dependent on amount of donor and independent of the amount acceptor impurity doping

c. Depend on amount of both donor & acceptor impurity doping

d. None of these



66. The snubber circuit used across SCR is a simple

a. R-L network

b. RLC network

c. LC network

d. RC network



67. To limit the rate of rise of SCR anode current a small

a. Inductor is inserted in cathode circuit

b. Inductor is inserted in anode circuit

c. Capacitor is inserted in anode circuit

d. Capacitor is inserted in cathode circuit



68. Torque developed by a DC servo motor is proportional to the

a. Product of power and time

b. Product of armature current and back emf

c. Armature voltage and armature current

d. Field voltage and field current



69. Proportional Integral control



a. Reduces steady state error but reduces the forward gain

b. Increases the forward gain and reduces the steady state error

c. Increases the steady state error and increases the forward gain

d. None of these



70. Increasing the servo bandwidth:

a. Improves signal to noise ratio

b. Improves speed response and lowers signal to noise ratio

c. Improves power output

d. None of these

Answers

b51. a52. c53. b54. b55. b56. b57. c58. d59. b60. c61. c62. b63. a64. a65. a66. d67. b68. b69. a70. b

71. Notch filter is

a. Low pass filter

b. High pass filter

c. Narrow stop band filter

d. Narrow pass band filter



72. In TV Receivers the Electron beam deflection method used is

a. Electro static

b. Electro magnetic

c. Magnetic

d. All the above



73. In a line of sight communication the maximum range R in miles between the receiver antenna and transmitter antenna of height H in feet is approximately

a. R = 1.93 ÖH

b. R = 1.23 ÖH

c. R = 1.53 ÖH

d. R = 2.03 ÖH



74. In wavelength of the 60 MHz carrier frequency is

a. 10 metres

b. 15 metres

c. 5 metres

d. 2.5 metres



75. In standard TV receiving antenna the dipole element is

a. 0.5 of the wave length

b. 0.25 of the wave length

c. 1.5 of the wave length

d. 1.0 of the wave length



76. The characteristics of FET are similar to:

a. Triode

b. Tertode

c. Pentode

d. Diode



77. Charge coupled device is an array of capacitors whose structure is similar to:

a. Shift register

b. Flip-flop

c. NAND gate

d. Amplifier



78. Operational amplifier characteristics are which of the following:

a. Infinite gain

b. Infinite input impedance

c. Output impedance is zero

d. All of the above



79. The typical value of the open loop gain in dB of an amplifier at DC with no feedback is:

a. 90 to 100

b. 80 to 90

c. 0 to 50

d. 50 to 70



80. The 3 dB band width means the frequency at which

a. The open loop voltage gain reduced to 0.707

b. The open loop gain reduced to unity

c. Maximum voltage of a signal is without distortion

d. It is a medium wave band width of radio receiver



81. Rise time of an amplifier is defined as time required

a. To change from 0 to 100 % of its final value

b. To change from 0 to 50 % of its final value

c. To change from 10 to 90 % of its final value

d. To change from 10 to 100 % of its final value



82. High speed amplifier design emphasized on

a. Extremely small bandwidth

b. Very slow response

c. Unity gain bandwidth after 10 MHz

d. None of these



83. Tuned amplifier having the frequency range between

a. 150 KHz – 50 MHz

b. 100 Hz – 100 KHz

c. 100 KHz – 120 KHz

d. 50 MHz – 100 MHz



84. The resonance frequency of a tuned circuit made up of R, L, C is given by

a. 1/2 pÖLC

b. 2 pÖLC

c. 2 p / ÖLC

d. ÖLC / 2



85. The voltage follower can be obtained using operational amplifier

a. Without any feedback

b. Series parallel feedback of unity

c. Parallel feedback

d. Series feedback



86. Fidelity of the amplifier is when

a. It is a linear amplifier

b. It does not add or subtract any spectral components

c. It amplifier each component by the same amount

d. All of the above



87. What would be the output when two input sine waves of frequency 50 KHz and 100 KHz passed through an amplifier in the medium signal

a. 50 KHz and 100 KHz

b. 100 KHz and 200 KHz

c. 50 KHz and 150 KHz

d. All of the above



88. The important application of Schmitt trigger is

a. To convert slowly varying input voltage to abrupt voltage change

b. To convert abruptly varying input voltage into slowly varying output

c. To change the frequency of the input

d. None of these



89. Meaning of decoding is

a. Binary addition

b. Data transmission

c. Demultiplexing

d. Storage of binary information



90. Approximately how many number of gates are incorporated in SSL chip

a. 12

b. 100

c. Excess of 100

d. Excess of 1000



91. The circuit diagram represents which one of the following

a. Half adder

b. Full adder

c. Exor gate

d. AND gate



92. Flip flop cannot be called as

a. Bistable multivibrator

b. 1 Bit memory unit

c. latch

d. combinational circuit



93. The important use of low pass filter in power supply is

a. To get the regulation in the output voltage

b. To filter out the ripple frequency

c. To increase the current rating

d. To convert AC into DC



94. Binary equivalent of the decimal number 145 is

a. 10010001

b. 1001011

c. 1010001

d. 1100010



95. In which of the following gate the output will be high when all the maintained at high level

a. NOR

b. AND

c. NAND

d. EXOR



96. Which of the following definition is true in the De Morgan’s theorem

a. Multiplication symbols are replaced by addition symbol

b. Addition symbols are replaced by Multiplication symbol

c. Each of the terms are expressed in the complementary form

d. All of the above



97. 8421/BCD code fro a decimal number 149 is

a. 0001 0100 1001

b. 10010101

c. 10101001

d. None of these



98. Combinational circuit are mainly characterized by

a. Output depends upon the previous state & presents state

b. Output depends upon the input at that particular instant

c. Output depends upon the presents state & the clock state

d. Output does not depends upon the input at all



99. A flip flop is defined as

a. A bistable device with two complementary outputs

b. It is memory element

c. It will respond to input and it is a basic memory element

d. All of the above



100. Four bit code is called

a. Nibble

b. Byte

c. Word

d. Register



Answer:-

.71. c72. c73. b74. c75. a76. c77. a78. d79. d80. a81. c82. c83. a84. a85. b86. d87. a88. a89. c

90. a91. a92. d93. b94. a5. b96. d97. a98. b9. d100.a

BEL Electronics and Computer Questions with answers

1. The register is a
1. Simplified unit of a subtractor
2. Cascaded group of the flip-flop
3. Binary ripple counter
4. Data selector


2. The energy of the photo electron depends upon the following factor
1. Intensity of incident radiation
2. Quality of the photocathode
3. Frequency of incident radiation
4. Type of the incident light source


3. Hall effect is used to determine
1. Magnetic flux
2. Current density
3. Type of semiconductor material
4. All of the above


4. Which one of the following is the thermistor
1. Semiconductor device
2. Microwave device
3. Platinum resistance thermometer
4. Thermo-couple device


5. Silicon is having direct band gap
1. True
2. False
3. No gap
4. None of these


6. Boron is doped in silicon to form
1. P-type
2. N-type
3. Intrinsic
4. None of these


7. The concentration of impurity in doped silicon semiconductor per atom is
1. 1018 b. 1022 c.108 d.10-22


8. Conduction in P-type semiconductor is due to
1. Movement of hole
2. Movement of electron
3. Movement of atoms
4. Movement of electron-hole pair


9. Slope of electrical conductivity Vs temperature in semiconductor is
1. Positive
2. Negative
3. Linear
4. No effect


10. Volt equivalent of temperature of silicon at room temperature (300 deg K) is
1. 0.7V b. 1.1V c. 0.026V d. 16V

Answer

1. b2. c3. d4. d5. a6. a7. a8. a9. b10.

11. Carbon is not used as semiconductor because
1. It does not belong to silicon group
2. It is a good conductor
3. It is not a conductor
4. Band gap is very high


12. In forward bias of P-N junction depletion region
1. Increases
2. Decreases
3. Remains the same
4. Breaks down


13. Knee voltage in diode stands for
1. Reverse break down voltage
2. Saturation voltage
3. Threshold of current conduction
4. Peak inverse voltage


14. An ideal semiconductor diode for an AC input acts like
1. Unidirectional switch
2. Bidirectional switch
3. Cuts off AC part
4. Power booster


15. Reverse saturation current in P-N junction diode is due to
1. Hole conduction
2. Electron conduction
3. Minority carrier conduction
4. Majority carrier conduction


16. In the zener diode the break down in the reverse characteristic current is due to
1. Electrons
2. Hole
3. Electron hole pair
4. Crystal ions


17. The percentage of voltage regulation is defined as
1. V no load " V load r100 / V load
2. V load " V no load r100 / V load
3. V load " V no load r100 / V no load
4. V no load r100 / V load


18. Filtering is effected by shunting the load with a
1. Capacitor
2. Resistor
3. Inductor
4. None of these


19. Without applying the biasing voltage the transistor current would be
1. Maximum
2. Minimum
3. No change
4. Zero


20. In the transistor the doping at the emitter is much larger than the base results in
1. Emitter current entirely of holes
2. Emitter current entirely of electrons
3. Base current is due to electron-hole pair
4. Emitter does contribute carrier which can reach collector
Answers
c11. b12. b13. c14. a15. c16. c17. a18. a19. b20.

21. The largest current carrying component in P-N-P transistor is
1. Electrons
2. Holes
3. Electron hole pair
4. Silicon atoms


22. The circuit shown in the figure represents
1. Rectifier
2. Clamping circuit
3. Clipping circuit
4. Low pass filter

23. Clamping circuit is used for
1. AC to DC conversion
2. Biasing
3. Limiting the amplitude
4. Wave shaping


24. For ideal clipping circuit one should use a diode with cut-in voltage
1. 0.7V b.1.1V c. 0V d. 0.2V


25. The ratio of peak inverse voltage of full wave and half wave rectifier is
1. 1 b. 2 c. 1/2 d. 1/4


26. Which of the following transistor configuration is a power amplifier
1. Common emitter
2. Common base
3. Common collector
4. All of the above


27. In a active mode of a transistor, collector conduction takes place due to
1. Majority carrier
2. Minority carrier
3. Common collector
4. All of the above


28. Common emitter configuration is used for a
1. Current amplification
2. Voltage amplification
3. Current and voltage amplification
4. Charge amplification


29. The transistor configuration where input is emitter and output is collector is called:
1. Common emitter
2. Common base common collector
3. Voltage follower(current gain)
30. Beta of a transistor is given by
1. Ib/Ic b. Ic/Ib c. Ib/Ie d. Ic/Ie

Answers
b21. b22. b23. c24. b25. a26. d27. a28. c29. b30.

31. Germanium transistor is preferred over silicon transistor in the following application
1. High frequency
2. High power
3. Low voltage
4. Power rectification


32. SCR is based on the principle of
1. Voltage regeneration
2. Current regeneration
3. Power regeneration
4. Power rectification


33. The number of clock pulses arriving at the digital counter input, should be in the form of
1. Decimal
2. Binary
3. Octal
4. Hexadecimal


34. In which of the counter the clock input is common to all flip flops
1. Asynchronous counter
2. Synchronous counter
3. Decade counter
4. Down counter


35. Multiplexer helps in which of the following
1. Repetition of similar circuit construction
2. Selecting all the signal at the output at the same time
3. Prevention of constructing similar circuits
4. Increase in the constructional costs due to repetition circuits


36. Full adder for two inputs can be developed with the help of
1. Two half adder on OR gate
2. One half adder and two OR gate
3. An EXOR gate and AND gate
4. Two AND gates and an OR gate


37. The important use of gray code is for a
1. Ripple counter
2. Full adder
3. Encoder
4. Decoder


38. In which of the code only one bit changes at each time
1. BCD
2. Aiken code
3. Excess 3 code
4. Gray code


39. In Johnson code for N bits, the maximum number can be formed is given by an expression
1. 2.N b. 2N c. 2N " 2N d. None of these
40. The active mode of transistor operation is used in log circuits because of its
1. Non linearity
2. Linearity
3. Switching nature
4. High speed
Answers

b31. b32. c33. b34. b35. a 36. a37. c38. d39. b40. a

41. Intermediate frequency in television receiver is
1. 26-46 MHz
2. 1.6-2.3 MHz
3. 455-KHz
4. None of these


42. At absolute temperature, a silicon crystal acts like an insulator because
1. Electrons cannot move through a crystal
2. Electrons are tightly held by other atoms
3. Electrons can break away only by supplying energy
4. All of the above


43. Extrinsic semiconductor is
1. Doped with impurities
2. Exists in the pure state
3. N-type only
4. Only P-type


44. The process of extracting the audio information from the modulated envelope is called
1. Modulation
2. Detection
3. Transmission
4. Oscillation


45. Selectivity of a radio receiver is defined as
1. Ability to reproduce the original frequencies
2. Ability to eliminate wanted frequencies
3. Ability to reject unwanted frequencies
4. Ability to pick up the weak signal


46. Digital counter cannot be used as
1. Clock
2. Timer
3. Event counter
4. Multiplier


47. Distortion in the amplifier is due to
1. Non linearity of the device
2. Inductance presents in the circuits
3. Capacitance
4. Stray effect


48. The purpose of RF amplifier tuning in the radio receiver is
1. To reject all the frequencies
2. To select all the frequencies
3. Only to select required frequencies & amplification
4. To vary the band width


49. The intermediate frequency used in the radio receiver is
1. 455KHz b. 1.6 MHz c. 20 MHz d. 60 MHz


50. The purpose of using tuned circuit between stages in the radio receiver is
1. To increase the selectivity
2. To increase the sensitivity
3. To increase both selectivity and sensitivity
4. To get the detector output

Answers
41. d42. d43. a44. b45. c46. d47. a48. c49. a50.

51. In an amplifier, the frequency characteristic may be divided into how many regions
1. Two b. Three c. Four d. Zero


52. Op.amp. has high input impedance because
1. High band width
2. Differential amplifier
3. Current source at input end
4. Common collector configuration


53. Gain of an OP amp. In inverting mode is "Rf / Rn provided, the OP.amp. has
1. Low output impedance
2. Low input bias current
3. High CMRR
4. High open loop gain


54. Slew rate of an OP.amp.is
1. Change of O/p voltage with time
2. Propagation speed
3. Input RC time constant
4. Off set voltage drift


55. Instrumentation OP.amp. is used in application where
1. Two instrument are to be interfaced
2. Input is very low level signal
3. DC signals are involved
4. Differential signals are involved


56. An OP.amp. integrater will be
1. Capacitor at input
2. Diode at input
3. Diode feed back
4. Capacitor feed back


57. A logarithmic amplifier will have
1. Inductor feed back
2. Diode feed back
3. Resistance feed back
4. Thermistor feed back


58. OP.amp. can be converted into capacitor by
1. Increasing bandwidth
2. Removing feed back
3. Increasing input impedance
4. Positive feed back


59. Comparators are used as
1. Switching device
2. Linear amplifiers
3. Power amplifiers
4. High speed amplifiers


60. Typical output impedance of 741 OP amps. is
1. 0.5 W b. 1 K W c. 1 W d. 75 W
Answers
51. c52. b53. d54. b55. b56. d57. d58. a59. a60. a

61. Typical unity gain bandwidth of 741 OP amps. is
1. 10 MHz b. 100 KHz c. 1 MHz d. 1.5 MHz


62. OP.amp. wein bridge oscillator works when the over all gain is
1. 180 b. 3 c. 1.2 d. 125


63. Important part in a electronic voltage regulator is
1. Error amplifier
2. External pass transistor
3. Reference voltage diode
4. All the above


64. To generate a triangular wave form from a square wave
1. Differentiator is used
2. Integrator is used
3. Logarithmic amplifier is used
4. Clipping circuit is used


65. For multiplying two analog signals which one of the following is used
1. Comparator
2. Hall effect device
3. Gunn diode
4. Tunnel diode


66. Which of the following device is used as an electronic memory element
1. Astable multivibrator
2. Monostable multivibrator
3. Magnetic tape
4. None of these


67. Phase sensitive detector in lock-in-amplifier is used
1. To increase the sensitivity of an instrument
2. To limit the bandwidth
3. To increase the dynamic range of the signal
4. To increase the input impedance


68. In television transmission video signal is
1. Frequency modulated
2. Amplitude modulated
3. Phase modulated
4. delta modulated


69. The Boolean function XYZ + YZ + XZ, after simplification gives
1. X b. Y c. Z d. X+Y+Z
70. Extremely low power dissipation and low cost per gate can be achieved in
1. MOS ICs
2. CMOS ICs
3. TTL ICs
4. ECL ICs
Answers
c61. a62. b63. d64. b65. a6. c7. b68. b69. c70. b

71. Which of the following digital IC families can give maximum fan-out
1. ECL b. PMOS c. HTL d. CMOS


72. A punched card has
1. 22 rows, 90 columns
2. 12 rows, 80 columns
3. 12 rows, 2 columns
4. 8 rows, 128 columns


73. Which one of the following is a 16 bit microprocessor
1. Zilog 80
2. Intel 8085
3. Motorola 6800
4. Intel 8086


74. (0.3125)10 when converted to base 8 gives
1. (0.16)8 b. (0.26)8 c. (0.24)8 d. (0.124)8


75. Excess " 3 code is a
1. Weighted code
2. Cyclic code
3. Error correcting code
4. Self complementing code


76. ASC II code is a
1. Error detecting code
2. Self correcting code
3. An alphanumeric code
4. A weighted code


77. Modulo " 2 addition is represented by
1. f = XY + XY
2. f = XY + XY
3. f = X + XY
4. f = XY + XZ + YZ


78. Which one of the following Boolean identities is correct?
1. XYZ + YZ + XZ = YZ + XZ
2. XYZ + YZ +XZ = XY + XZ
3. XY +XZ = XY + XZ + YZ
4. X + XY = XY


79. SN7410 IC is a
1. Quad 2 input NAND gate
2. Triple 3 input NAND gate
3. Dual M/S J-K flip flop
4. None of these


80. Intel 8085 microprocessor has two registers known as primary data pointers these are
1. Registers V & C
2. Registers D & E
3. Registers H & L
4. None of these


81. Intel 8080 microprocessor has an instruction set of 91 instructions. The op-code to implement the instruction set should be at least
1. 6 bit b. 7 bytes c. 7 bit d. 8 bit


82. A micro programmed computer can have the following memories in its control memory unit
1. Semiconductor ROM
2. Semiconductor RAM
3. Magnetic RAM
4. None of these


83. In digital circuits parallel operation is preferred because
1. It requires less memory
2. Circuitry is simple
3. It is faster than series operation
4. For None of these of the above reasons


84. SN 7401 IC is a
1. Quad 2 input NAND gate
2. Quad 2 input NAND gate with open collector output
3. Quad single input NAND gate with open collector output
4. None of these


85. What is the binary code of (26)?
1. 11001 b. 10001 c. 11010 d. 10100


86. The basic RS flip flops is
1. A bistable multivibrator
2. A monostable multivibrator
3. An astable multivibrator
4. None of these


87. The input impedance of an operational amplifier is
1. Very small
2. Zero
3. Very high but not infinite
4. Infinite


88. Sn 7411 is
1. OP.amp. monolithic and short circuit protection in-built
2. Two input NAND gate
3. Three input NAND gate with open collector output
4. None of these


89. The output voltage of an operational amplifier is
1. 90 deg out of phase from the input
2. 90 deg out of phase from the input
3. 45 deg out of phase from the input
4. 180deg out of phase from the input
90. The equivalent octal number of (492) is
1. 574 b. 547 c. 754 d. 758


Answers
71. d72. b73. d 74. c75. d76. c77. a78. c79. b80. c81. c82. a83. b84. b85. c86. a87. c88. c89. d90. c

91. The equivalent decimal number for gray code 1011 is
1. 14 b. 13 c. 41 d. 31


92. The output will be only if all inputs go to 1 in case of
1. OR gate b. AND gate c. NAND gate d. NOT gate


93. Which of the following circuits is known as half adder?
1. AND circuit
2. OR circuit
3. Exclusive OR circuit
4. None of these


94. Which of the following memories is used to store variable quantities of the data?
1. RAM b. ROM c. PROM d. EPROM


95. Large scale Integrated (LSI) circuits usually contain
1. Less than 10 gates
2. 10 to 100 gates
3. more than 100 gates
4. more than 1000 gates


96. The Boolean expression A + AB + B on simplification can be reduced to:
1. 0 b. 1 c. A + B d. A + B


97. For realizing a decade counter using flip-flops the minimum number of flip-flops required is
1. 4 b. 5 c. 6 d. 10


98. Which logic family is widely used in SSI & MSI applications?
1. ECL b. DTL c. TTL d. None of these


99. An amplitude modulation detector detects
1. The peak value of the modulation signal
2. The envelop of the modulation signal
3. The peak value of the carrier signal
4. The average value of the carrier signal


100. Microwave (MW) links are generally preferred to coaxial cable for TV transmission because:
1. They have less overall phase distortion
2. They are cheaper
3. Of their greater bandwidth
4. Of their relative immunity to impulse noise.
91. b92. b93. c94. a95. c96. b97. a98. c99. b100. a

BEL Previous Year Questions with Answers

1. Transition capacitance Ct of a Varicap diode with Knee voltage Vt, reverse voltage Vr and K, the constant based on semiconductor material and the construction technique & N dependent on type of junction is given by

a. 1 / K (Vt + Vr)N/2

b. 1 / K (Vt + Vr)N

c. K / (Vt + Vr)N

d. K / (Vt + Vr)1/N

Answer : c



2. Ct = K / (Vt + Vr)N where Vt Knee voltage, Vr reverse voltage, K manufacturing dependent constant and N dependent on type of junction, for alloy junction the value of N is

a. 1/3

b. 2/3

c. 1/2

d. 1/4

Answer : c

3. The distortion less output characteristic of a network means

a. Constant amplitude and linear phase shift over frequency

b. Linear phase shift and amplitude need not be constant

c. Any amplitude and phase

d. None of these

Answer : a



4. Single sideband means suppressed

a. Carrier

b. Carrier and one side band

c. One side band

d. None of these

Answer : b



5. In an amplitude modulated signal, lower side band frequency is equal to (if the carrier frequency is fc and modulation frequency is fm)

a. fm + fc

b. fc – fm

c. fm r fc

d. fc / fm

Answer : b



6. The noise figure of a receiver is a measure of:

1. Excess noise generated

2. Bandwidth of the receiver

3. Gain of the receiver

4. Operating frequency

Answer :1



7. The ratio receiver is:

1. Direct detection type

2. Super regenerative type

3. Super heterodyne type

4. None of these

Answer : 3



8. In an amplitude modulation system, the modulation index is dependent upon:

1. Modulating frequency only

2. Carrier amplitude only

3. Modulating signal amplitude only

4. Modulating and carrier amplitudes only

Answer : 2



9. Image rejection mixer is generally used:

1. To reject the unwanted signal

2. To improve signal amplitude

3. To improve noise figure

4. To improve conversion loss

Answer : 3



10. The value of a resistor creating thermal noise is doubled. The noise power generated is therefore:

1. Halved

2. Quadrapuled

3. Doubled

4. Unchanged

Answer : 2

11. Ct = K / (Vt + Vr)N where Vt Knee voltage, Vr reverse voltage, K manufacturing dependent constant and N dependent on type of junction, for diffused junction the value of N is

a. 1/3

b. 2/3

c. 1/2

d. 1/4

Answer : a



12. In JFET, the drain current Id is given by (Idss drain – source saturation current Vgs – Gate – source voltage, Vp the pinch off voltage)

a. Idss[1 – Vp/Vgs]

b. Idss(1 – Vgs/Vp)2

c. Idss[1 – Vgs/Vp)

d. Idss(1 – Vgs/Vp)3/2

Answer : b



13. The shadow mask in colour tube is used to

a. Reduce X-Ray emission

b. Ensure each beam hits its own dots

c. Increase screen brightness

d. Provide degaussing for the screen

Answer : b



14. Indicate which of the following signal is not transmitted in colour TV

a. Y

b. Q

c. R

d. I

Answer : c



15. Another name for horizontal retrace in TV receiver is the

a. Ringing

b. Burst

c. Damper

d. Fly back

Answer : d



16. Another name for the colour sync in the colour TV system

a. Ringing

b. Burst

c. Damper

d. Fly back

Answer : b



17. The HV anode supply for a picture tube of a TV receiver is generated in the

a. Mains transformer

b. Vertical output stage

c. Horizontal output stage

d. Horizontal oscillator

Answer : c



18. The output of vertical amplifier is

a. Direct current

b. Amplified vertical sync pulse

c. A saw tooth voltage

d. A saw tooth current

Answer : d



19. In a transistor if Alpha = 0.98, current gain is equal to

a. 29

b. 59

c. 69

d. 49

Answer : d



20. The active region in the common emitter configuration means

a. Both collector and emitter junction is reverse biased

b. The collector junction is forward biased and emitter junction

c. The collector junction is reverse biased and emitter junction is forwared biased

d. Both collector & emitter junction are forward biased

Answer : c



21. The saturation region in the common emitter configuration means that

a. Both collector & emitter junction are reverse biased

b. The collector junction is forward biased and emitter junction

c. The collector junction is reverse biased and emitter junction is forwared biased

d. Both collector & emitter junction are forward biased

Answer : d



22. The % of Red, Green & Blue in 100% White Y is given by

a. 30%, 59%, 11%

b. 50%, 30%, 11%

c. 30%, 11%, 50%

d. 33.3%, 33.5%, 38.3%

Answer : a



23. Equalizing pulse width, if H is the Horizontal sync rate

a. 0.64 H

b. 0.07 H

c. 0.04 H

d. 0.16 H

Answer : c



24. In a simple RC network the bandwidth is equal to

a. 1/2 p RC

b. RC / 2

c. 2 C / p R

d. 2 p / RC

Answer : a



25. The time constant of a RC network is given by

a. RC

b. C/R

c. R/C

d. None of these

Answer : d



26. First zero crossing of pulse frequency spectrum occurs at if d is the pulse width, T is the pulse repetition rate

a. 1/d

b. d/T

c. T/d

d. T

Answer : a



27. Indicated the false statement:

1. HF mixer are generally noisier than HF amplifier

2. Impulse noise voltage is independent of bandwidth

3. Thermal noise is independent of the frequency at which it is measured

4. Industrial noise is usually of the impulse type

Answer : 2



28. If the carrier of a 100 percent modulated AM wave is suppressed the percentage power saving will be:

a. 50

b. 70

c. 100

d. 66.6

Answer : d



29. A balanced modulator produces:

1. The carrier and Two side bands

2. The carrier and one side band

3. Two side bands alone

4. Carrier and a number of side bands

Answer : 3



30. The frequency deviation in FM system is proportional to:

1. Modulating frequency

2. Carrier amplitude

3. Modulating signal amplitude

4. None of these

Answer : 3



31. In FM, the total transmitted power is:

1. Dependent on modulating signal amplitude

2. Dependent on modulating frequency

3. Dependent on modulating index

4. Independent of the above

Answer : 4



32. A quarter wave line when short circuited at the far end behaves like

1. Pure inductor

2. Pure capacitor

3. Parallel tuned circuit

4. Series tuned circuit

Answer : 3



33. The stub line used to match transmission line with a given load impedance is generally

1. Another open circuited line

2. Another short circuited line

3. Quarter wave transmission line

4. Half wave transmission line

Answer : 2



34. The smith chart generally covers a distance of

1. Quarter wavelength

2. Half wavelength

3. One wavelength

4. Twice the wavelength

Answer : 2



35. The component generally used to sample a portion of the energy transmitted in a line is

1. Isolator

2. Circulator

3. Directional coupler

4. None of these

Answer : 3



36. The return loss in a transmission line is a measure of

1. Loss of the line

2. Standing wave ratio

3. Characteristic impedance of the line

4. None of these

Answer : 2



37. The antenna can be considered as

1. Matching the source and free space

2. Matching the source to the line

3. Matching the line and free space

4. None of these\

Answer : 3



38. The free space impedance is approximately equal to

1. 177 W

2. 277 W

3. 377 W

4. 50 W

Answer : 3



39. The polarization refers to

1. The physical orientation of the radiated wave

2. The directional of propagation of the wave

3. Direction perpendicular to the propagation of the wave

4. None of these

Answer : 3



40. If u & e are the permeability and permittivity respectively the characteristic impedance of the medium is given by

a. ue

b. Öu/e

c. Öe/u

d. Öeu

Answer : 2



41. The power density at distance ‘r’ from an isotropic radiator with transmitted power P is:

1. P/r2

2. P/2 p r2

3. P/4 p r2

4. None of these

` Answer : 3



42. The carrier in an FM system disappears for the lowest modulation index of:

a. 0.5

b. 1.0

c. 2.4

d. 3.5

Answer : c



43. The difference between phase and frequency modulation:

1. Is purely theoretical because they are the same in practice

2. Is too great to make the two systems compatible

3. Lies in the poorer audio response of phase modulation

4. Lies in the different definition of the modulation index

Answer : 4



44. The overall noise figure of two cascaded amplifiers is equal to

1. The algebraic sum of the two

2. The sum of the squares of the two

3. The square root of the product of the two

4. None of these

Answer : 4



45. The noise power output of an amplifier is equal to:

1. KTo BFG

2. KTo FG

3. KTo F/G

4. KTo / FG

Answer : 1



46. The effective noise temperature of an amplifier is equal to

1. (F + 1) To

2. FTo

3. (F – 1) To

4. None of these

Answer : 3



47. The noise figure of an amplifier depends upon

1. Its bandwidth

2. Its gain

3. Its operating frequency

4. None of these

Answer : 4



48. The velocity of electromagnetic wave in a coaxial cable is

1. Equal to the velocity in free space

2. Less than the velocity in free space

3. Greater than the velocity in free space

4. None of these

Answer : 2



49. The standing wave ratio [SWR] in a transmission line:

1. Is proportional to the load impedance

2. Is dependent on the source impedance

3. Is a mis-match between the load and line

4. Is a measure of its power handling capability

Answer : 3



50. The standing wave ratio (SWR) is unity in a transmission line if

1. The load impedance is equal to the characteristic impedance of the line

2. The load impedance is twice that of the characteristic impedance

3. The load impedance is half of the characteristic impedance of the line

4. None of these

Answer : 1



51. The standing wave voltage node along a line repeats at the rate of if L is the wave length

a. L/4

b.L/2

c.L

d.2L

Answer : 2





52. FM modulation becomes equivalent to AM modulation if

1. FM index is greater than 1

2. FM index is equal to 1

3. FM index is very much less than 1

4. FM index less than or equal to 1

Answer : 3



53. S/N improvement of FM over AM, B is the FM modulation index

a. 3B2

b.B

c.2B

d.B/2

Answer : a



54. Picture transmission in TV employs

1. Suppressed carrier modulation

2. Vestigial side band

3. Single side band

4. None of these

Answer : 2



55. Sound transmission in TV employ

1. Amplitude modulation

2. Phase modulation

3. Frequency modulation

4. Pulse amplitude modulation

Answer : 3



56. One of the following is an indirect way of generating FM this is the:

1. Reactance FET modulator

2. Varacter divide modulator

3. Amstrong modulator

4. Reactance bipole transistor modulator

Answer : 3



57. The modulation index of AM wave is changed from 0 to 1. The transmitted power is

1. Un-changed

2. Halved

3. Doubled

4. Increased by 50%

Answer : 4



58. The isotropic antenna is represented by

1. Dipole antenna

2. Rhombic antenna

3. Yagi uda antenna

4. No such antenna exists in practice

Answer : 4



59. The gain of parabolic reflector antenna is proportional to

1. The diameter of the reflector

2. Square of the diameter of the reflector

3. Aperture area of the feed

4. None of these

Answer : 2



60. The parabolic reflector antenna are generally used to

1. Provide high gain

2. Provide pencil beam

3. Increase bandwidth of operation

4. None of these

Answer : 2



61. Cassegrain feed is used with a parabolic reflector to

1. Increase gain of the system

2. Increase the bandwidth of the system

3. Reduce the size of the main reflector

4. Allow the feed to be placed at a convenient point

Answer : 4



62. A helical antenna is used for satellite tracking because of its

1. Circular polarization

2. Maneuverability

3. Broad bandwidth

4. Good front – to – back ratio

Answer : 1



63. The discone antenna is

1. A useful direction finding antenna

2. Used as a radar receiving antenna

3. Circularly polarized like other circular antenna

4. Useful as a VHF receiving antenna

Answer : 4



64. Waveguides are used mainly for microwave signals because

1. They depend on straight line propagation which applies to microwaves only

2. Losses would be too heavy at lower frequencies

3. There are no generators powerful enough to excite them at lower frequencies

4. They would be too bulky at lower frequencies

Answer : 4



65. The wavelength in a waveguide

1. Is greater than in free space

2. Depends only on the waveguide dimensions and the free-space wavelength

3. Less than the free space wavelength

4. Equal to the free space wavelength

Answer : 1



66. The dominant mode of propagation is preferres with rectangular waveguide because(indicate false statement)

1. It leads to the smallest waveguide dimensions

2. The resulting impedance can be matched directly to coaxial lines

3. It is easier to excite than the other modes

4. Propagation of it without any spurious generation can be ensured

Answer : 2



67. The velocity of propagation (group velocity) in a waveguide is

1. Less than the free space velocity

2. Greater than the free space velocity

3. Equal to be free space velocity

4. None of these

Answer : 1



68. A wave can propagate in a waveguide if its cut off wavelength is

1. Greater than the free space wavelength

2. Less than the free space wavelength

3. Equal to be free space wavelength

4. None of these

Answer :3



69. The dominant mode in a rectangular waveguide is

a. TE11

b. TE10

c.TE20

d.TM11

Answer : 2



70. The characteristic wave impedance of a waveguide

1. Depends on the mode of propagation

2. Does not depend on the mode of propagation

3. Is same as the free space impedance

4. None of these

Answer : 1



71. A choke flange may be used to couple two waveguides

1. To help in the alignment of the waveguides

2. Because it is simpler than any other joint

3. To compensate the discontinuities at the joint

4. To increase the bandwidth of the system

Answer : 2



72. Frequencies in the UHF range is normally propagated by means of

1. Ground waves

2. Sky waves

3. Surface waves

4. Space waves

Answer : 4



73. As electromagnetic waves travel in free space, only one of the following can happen to them

1. Absorption

2. Attenuation

3. Reflection

4. Refraction

Answer : 2



74. High frequency waves are

1. Absorbed by the F2 layer

2. Reflected by the D layer

3. Affected by the solar cycle

4. Capable of use for long distance communications on the moon

Answer : 3



75. Indicate which one of following terms applies to troposcatter propagation

1. SIDS

2. Fading

3. Fraday rotation

4. Atmospheric storms

Answer : 2



76. When microwave signals follow the curvature of the earth, this in known as

1. Faraday effect

2. Ducting

3. Ionospheric reflection

4. Tropospheric scattering

Answer : 2



77. An ungrounded antenna near the ground:

1. Is unlikely to need an earth mat

2. Acts as a single antenna of twice the height

3. Must be horizontally polarized

4. Acts as an antenna array

Answer : 4



78. One of the following consists of non-resonant antenna:

1. The folded dipole

2. The rhombic antenna

3. The end fire array

4. The broad side array

Answer : 2



79. Balun is:

1. A circuit element to connect balance line to unbalanced antenna or line:

2. A circuit element to connect balance line to balanced line

3. A circuit element to connect unbalance line to unbalanced line

4. None of these

Answer : 1



80. The slotted line is used to measure:

1. Standing wave ratio

2. Load impedance

3. Source impedance

4. None of these

Answer : 1



81. In amplitude modulation Ec ( 1 + m Sin Wmt) Sin Wot, each side band amplitude will be:

1. Ecm/2

2. Ecm

3. Ec/m

4. 2Ec/m

Answer : 1





82. The dominant mode in a circular waveguide is

a. TE01

b.TE11

c.TM01

d.TM11

Answer : 3



83. A ferrite is

1. A non-conductor with magnetic properties

2. An inter metallic compound with particularly good conductivity

3. An insulator which heavily attenuates magnetic fields

4. A microwave semiconductor invented by farady

Answer : 1



84. The maximum power that may be handled by a ferrite component is limited by the

1. Curie temperature

2. Saturation magnetization

3. Line width

4. Gyro magnetic resonance

Answer : 1



85. The isolator is

1. Bidirectional

2. Unidirectional

3. Used to tap the power in a waveguide transmission line

4. Used for None of these of the above

Answer : 2



86. Isolator is generally used:

1. To protect the high power transmitter

2. To protect receiver

3. To protect the antenna

4. To avoid arcing in waveguides

Answer : 1



87. A TR tube is used

1. To protect the high power transmitter

2. To protect receiver

3. To avoid arcing in waveguides

4. For None of these of the above

Answer : 2



88. Rieke diagrams are used to select best operating conditions for

1. TWT amplifier

2. Klystron oscillator

3. Magnetron oscillator

4. Cross field amplifiers

Answer : 3



89. The gain bandwidth product of a microwave transistor FT, is the frequency at which the

1. Alpha of the transistor falls by 3 dB

2. Beta of the transistor falls by 3 dB

3. Beta of the transistor falls to unity

4. Power gain of the transistor falls to unity

Answer : 1



90. The cavity magnetron uses strapping to

1. Prevent mode jumping

2. Prevent cathode-back heating

3. Ensure bunching

4. Improve the phase-focussing effect

Answer : 4



91. The transferred – electron bulk effect occurs in

1. Germanium

2. Gallium arsenide

3. Silicon

4. Metal semiconductor junction

Answer : 2



92. One of the following is not used as a microwave mixer or detector

1. Crystal diode

2. Schottky – barrier diode

3. Backward diode

4. PIN diode

Answer : 4



93. SAW devices may be used as:

1. transmission media like stripline

2. filters

3. UHF amplifiers

4. Oscillators at millimeter frequencies

Answer : 2



94. Surface acoustic waves propagate in:

1. Gallium arsenide

2. Indium phosphide

3. Stripline

4. Quartz crystal

Answer : 4



95. A parametric amplifier has an input and output frequency of 2.25 GHz, and is pumped at 4.5 GHz is a

1. Traveling wave amplifier

2. Degenerate amplifier

3. Lower-side band up converter

4. Upper-side band up converter

Answer : 2



96. The negative resistance in a tunnel diode

1. Is maximum at the peak point of the characteristic

2. Is available between the peak and valley points

3. Is maximum at the valley point

4. May be improved by the reverse bias

Answer : 2



97. Microwave links repeaters are typically 50KM apart

1. Because of atmospheric attenuation

2. Because of output tube power limitations

3. Because of Earth’s curvature

4. To ensure that the applied voltage is not excessive

Answer : 3



98. Microwave links are generally preferred to coaxial for television transmission because

1. They have less overall phase distortion

2. They are cheaper

3. Of their greater bandwidths

4. Of their relative immunity to impulse noise

Answer : 1



99. A geostationary satellite

1. Is motionless in space(except for its spin)

2. Is not really stationary at all, but orbits the earth with a 24 hour period

3. Appears stationary over Earth’s magnetic pole

4. Is located at a height of 35800KM to ensure global coverage

Answer : 2



100. The geostationary satellite launched by India are called

1. INTELSAT

2. INSAT

3. COMSAT

4. MARISAT

Answer : 2



101. After a target has been acquired the best scanning system for tracking is

1. Nodding

2. Spiral

3. Conical

4. Helical

Answer : 3



102. The Doppler frequency increases as the target

1. Approaches the radar

2. Recedes the radar

3. Moves perpendicular to the beam

4. Does not depend on the target velocity

Answer : 1

103. The Doppler effect is used in (indicate the false statement)

1. Moving target plotting on the PPI

2. MTI system

3. FM Radar

4. CW Radar

Answer : 1



104. Solution to the blind speed problem is to

1. Change the Doppler frequency

2. Vary the PRF

3. Use monopulse

4. Use MTI

Answer : 2



105. The A-scope displays

1. Target position and range

2. Target range but not position

3. Target position but not range

4. Neither range nor position but only velocity

Answer : 2



106. In the colour television system the sub carrier frequency in MHz is approximately

a. 3.58

b.4.5

c. 45.75

d. 5.58

Answer : a



107. In television 4: 3 : represents

1. The interlace ratio

2. The maximum horizontal deflection

3. Aspect ratio

4. The ratio of the two diagonals of picture tube

Answer : 3



108. Equalizing pulses in TV are sent during the:

1. Horizontal blanking

2. Vertical blanking

3. The serrations

4. Horizontal retrace

Answer : 2



109. The number of lines per field in Indian television system is:

a. 625

b. 312.5

c. 525

d. 262.5

Answer : 2



110. The number of frames in Indian TV system is:

a. 50

b. 60

c. 25

d.30

Answer : a



111. In a TV receiver the colour killer:

1. Cuts off the chromastages during monochrome reception

2. Ensures that no colour is transmitted to monochrome receivers

3. Prevents colour overloading

4. Makes sure that the colour burst is not mistaken for sync pulses

Answer : 1



112. A parametric amplifier must be cooled

1. Because parametric amplification generates a lot of hest

2. To increase bandwidth

3. Because it cannot operate at room temperature

4. To improve the noise performance

Answer : 4



113. If the peak transmitted power in a Radar system is increased by a factor of 16, the maximum range will be increased by a factor of

a. 2

b. 4

c.8

d. 16

Answer : d



114. Telephone traffic is measured

1. With echo

2. By relative congestion

3. In terms of the grade of service

4. In erlangs

Answer : 1



`115. If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of:

a. O2

b. 2

c. 4

d. 8

Answer : c



116. A high PRF will (indicate the false statement)

1. Make the returned echoes easier to distinguish from noise

2. Make target tracking easier with conical scanning

3. Increase the maximum range

4. Have no effect on the range resolution

Answer : 3



117. The bandwidth of a radar receiver is inversely proportional to the

1. Pulse width

2. Pulse repetition frequency

3. Pulse interval

4. Square root of the peak transmitted power

Answer : 1



118. If d is the pulse width, T is pulse repetition period and P is the peak power, the duty ratio is

a. T/d

b.P/T

c.P/d

d.d/T

Answer : d



119. If d is the duty ratio and P is the peak power in a pulsed transmitter, then the average power is

a. P.d

b. P.2d

c.P/d

d. P/2d

Answer : a



120. If the return echo arrives after the allocated pulse interval

1. It will interfere with operation of the transmitter

2. The receive might be overloaded

3. It will not be received

4. The target will appear closer than it really is

Answer : 4



ROUND 2



1How many of the integers between 25 and 45 are even?

A) 21

B) 20

C) 11

D) 10

E) 9



2 If taxi fares were Rs.1.00 for the first 1/5 mile and Rs.0.20 for each 1/5 miles thereafter, the taxi fare for a 3-mile ride was

A) Rs.1.56

B) Rs.2.40

C) Rs.3.00

D) Rs.3.80

E) Rs.4.20



3. A computer routine was developed to generate two numbers (X, Y) the first being a random number between 0 and 100 inclusive, and the second being less than or equal to the square root of the first. Each of the following pairs satisfies the routine EXCEPT

A) (99.10)

B) (85.9)

C) (50.7)

D) (1.1)

E) (1.0)



4. A warehouse had a square floor with are 10,000 sq. metres. A rectangular addition was built along one entire side of the warehouse that increased the floor by one-half as much as the original floor. How many metres did the addition extend beyond the original building?

A) 10

B) 20

C) 50

D) 200

E) 500



5. A digital wristwatch was set accurately at 8.30 a.m. and then lost 2 seconds every 5 minutes. What time was indicated on the watch at 6.30 p.m. of the same day if the watch operated continuously that time?

A) 5:56

B) 5:58

C) 6.00

D) 6:23

E) 6:20



6. A 5 litre jug contains 4 litres of a saltwater solution that is 15 percent salt. If 1.5 litres of the solution spilts out of jug, and the jug is then filled to capacity with water, approximately what percent of the resulting solution in the jug is salt?

A).5%

B) 9.5%

C) 10.5%

D) 12%

E) 15%

7. It was calculated that 75 men could complete a piece of work in 20 days. When work was scheduled to commence, it was found necessary to send 25 men to another project. How much longer will it take to complete the work?



8. A student divided a number by 2/3 when he required to multiply by 3/2. Calculate the percentage of error in his result.



9. A dishonest shopkeeper professes to sell pulses at the cost price, but he uses a false weight of 950gm. for a kg. His gain is …%.



10. A software engineer has the capability of thinking 100 lines of code in five minutes and can type 100 lines of code in 10 minutes. He takes a break for five minutes after every ten minutes. How many lines of codes will he complete typing after an hour?



11.There are total 15 people. 7 speaks french and 8 speaks spanish. 3 do not speak any

language. Which part of total people speaks both languages?



Ans: 1/5



12. A jogger wants to save ¼th of his jogging time. He should increase his speed by how much %age?



Ans: 33.33 %



13. a is an integer. Dividing 89 & 125 gives remainders 4 & 6 respectively. Find a ?



Ans: 17





14. A Child is saying numbers 1, 2, 3, 4. When he says 1 Another child puts white marble in a box. On saying 2 he puts Blue marble and on saying 3 he puts red marble. When child says 4 other child take out white and blue marble. Child says some no. in a sequence then questions are based on the no. of marbles in the box. Like this

1,1,2,3,1, 4, 1,1,3,2,2,4,111…



a) Find the no. of Blue marble in the box

b) Find the no. of White

c) No. of red marbles



15 A man crosses a circle of perimeter 35 m in 44 sec and he runs a hexagon of 42 m side. In how many second he finishes the complete perimeter of the hexagon?



16. A+b do a work in 6 days. A+c do the work in 10 days, c+a in 7.5 days. How manydays will it take for a+b+c to do the work and also find the number of days required by a alone?



17. Complete the series 7 49 56 392………….





18. A regular hexagon is inscribed in a circle. What is the perimeter of the hexagon in relation with the radius of the circle?



19. A circular path has a perimeter of 120m.a, b,c travel at 5 7 15m/s respectively. They start simultaneously. At what time do they meet next?



20. Totally there are 12 pipes. Some pipes fill the tank and some empties the tank (data will be given). If all the pipes are opened simultaneously when will the tank be filled?



21.Average age of 24 students is 36. When the age of teacher is added the average age is increased by 1 year. What is the age of the teacher?



22. Water and milk are mixed in the ratio 2:1,5:3 and 9:4.when all the mixtures of equal volume are mixed together what is the ratio water and milk in the resulting solution?



23. Average rate of five orange and four apples is 12 and 7 orange and 8 apples are 86. Find the total rate of 24 orange and 24 apples.



24.In how many ways the letters in the word MANAGEMENT can be arranged such that A’s does not come together?



25. A give B a start of 20 sec and leads by 20m. When he starts off 25 sec he finishes at the same time. What is the speed of A. (wordings not sure)?

25) A father has six children .all the children are born at regular intervels.if the sum of their ages of all the children and father is 186. calculate the age of the elder son, when the younger sons age is 3?



26. A man was engaged on a job for 30 days on the condition that he would get a wage of Rs. 10 for the day he works, but he have to pay a fine of Rs. 2 for each day of his absence. If he gets Rs. 216 at the end, he was absent for work for ... days.



27. A contractor agreeing to finish a work in 150 days, employed 75 men each working 8 hours daily. After 90 days, only 2/7 of the work was completed. Increasing the number of men by ________ each working now for 10 hours daily, the work can be completed in time.



28. Rs 50000 is divided into two parts

One part is given to a person with 10% interest and another part is given to a person with 20 % interest.At the end of first yearn he gets profit 7000 . Find money given by 10% ?



29. Time shown by a watch is 2.20 .Find the angle between them ?



30. Avg cost of 5apples+4 mangoes=rs.36

Avg cost of 7 apples + 8 mangoes=rs.48

Find total cost of 24 mangoes and 24 apples?