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SSC Scientific Assistant (IMD) Exam : Held on 22 Nov 2017 Shift-1 (ELECTRONICS)

SSC Scientific Assistant (IMD) Exam : Held on 22 Nov 2017 Shift-1

(ELECTRONICS)

QID : 501 - A resistance has colour-coded value of 500 ohms with ±15 % tolerance. What is the range (in ohms) in which actual resistance of this resistor can vary?

1) 425 to 575
2) 470 to 530
3) 485 to 515
4) 350 to 650

Correct Answer: 425 to 575

QID : 502 - What will be the current carrying capacity of a wire when its radius is doubled?

1) Current carrying capacity becomes one-fourth of the original value.
2) Current carrying capacity becomes one-sixth of the original value.
3) Current carrying capacity remains same.
4) Current carrying capacity becomes four times of the original value.

Correct Answer: Current carrying capacity becomes four times of the original value.

QID : 503 - Which of the following are active components?

I. Resistor
II. Capacitor
III. Independent voltage source
IV. Dependent current source

1) I only
2) I and III only
3) II and III only
4) III and IV only

Correct Answer: III and IV only

QID : 504 - When a sample of silicon and germanium material, having same impurity concentration, is kept at 30 degree Celsius then,______________.

1) both will have equal value of resistivity.
2) both will have equal positive resistivity.
3) both will have equal negative resistivity.
4) resistivity of germanium will be lower than that of silicon.

Correct Answer: resistivity of germanium will be lower than that of silicon.

QID : 505 - Which of the following is the SI unit of Inductance?

1) Tesla
2) Henry
3) Farad
4) Ohms

Correct Answer: Henry

QID : 506 - What does the line (|) in the symbol of a diode signifies?

1) n-type material (anode)
2) n-type material (cathode)
3) p-type material (anode)
4) p-type material (cathode)

Correct Answer: n-type material (cathode)

QID : 507 - A 9.6 V Zener diode shows its nominal voltage when a test current of 30 mA is passed through it. The incremental resistance at this particular value of current is found to be 6 ohms. Calculate the breakdown voltage (in Volts) of Zener diode model.

1) 9.364
2) 9.465
3) 9.582
4) 9.679

Correct Answer: 9.582

QID : 508 - Name the circuit which removes the negative part of the waveform.

1) Limiter
2) Negative clamper
3) Positive clamper
4) Negative clipper

Correct Answer: Negative clipper

QID : 509 - What is the ripple frequency (in Hz) of a full wave center-tap rectifier when it is supplied by a supply of frequency 110 Hz?

1) 50
2) 55
3) 60
4) 220

Correct Answer: 220

QID : 510 - A 16 V DC supply is used to power an LED having rating 1.6 V and 25 mA. What is the minimum value of series resistance (in ohms) required for safe operation of the LED?

1) 576
2) 584
3) 625
4) 656

Correct Answer: 576

QID : 511 - For an NPN-transistor, the value of alpha (α) is 0.99. Calculate the value of beta (β).

1) 0.99
2) 49
3) 99
4) 100

Correct Answer: 99

QID : 512 - What is the pinch off voltage (in Volts) of an n-channel enhancement mode MOSFET having threshold voltage of 0.5 V when it is subjected to a gate voltage of 5 V?

1) 2.5
2) 3
3) 3.5
4) 4.5

Correct Answer: 4.5

QID : 513 - In which of the following semiconductor devices, the path for carriers (electrons and holes) is not present initially but is developed during the operation?

1) BJT
2) D-MOSFET
3) E-MOSFET
4) JFET

Correct Answer: E-MOSFET

QID : 514 - The maximum power dissipation of a BJT is calculated as 0.4 W at 25 degree Celsius having derating factor of 0.0025 W/degree Celsius. What will be the maximum power dissipation (in W) at 50 degree Celsius?

1) 0.3375
2) 0.3975
3) 0.4025
4) 0.4625

Correct Answer: 0.3375

QID : 515 - Which among the following electronic devices contains silicon dioxide layer?

1) JFET
2) MOSFET
3) NPN transistor
4) PNP transistor

Correct Answer: MOSFET

QID : 516 - Which of the following BJT circuit has a voltage gain approximately equal to one?

1) Common base
2) Common emitter
3) Emitter follower
4) Collector follower

Correct Answer: Emitter follower

QID : 517 - Which of the following is correct about gain of a cascade amplifier?

1) Total gain is difference of individual gains.
2) Total gain is product of voltage and current gains.
3) Total gain is ratio of individual gains.
4) Total gain is sum of individual gains.

Correct Answer: Total gain is sum of individual gains.

QID : 518 - What is the reason for the use of RC coupling in low-level audio amplifiers?

1) It has better low frequency response than other amplifiers.
2) It does not need any adjustment.
3) The output is in phase with input signal.
4) Requires less voltage for operation.

Correct Answer: It does not need any adjustment.

QID : 519 - What is the percentage load regulation if a voltage regulation having no-load output of 20 V, has a full-load output of 18.5 V?

1) 0.044
2) 0.052
3) 0.074
4) 0.081

Correct Answer: 0.081

QID : 520 - What is the overall gain of the system if the output of the amplifier which has a gain of 10 is negatively feedback to input through another amplifier having gain of 5?

1) 0.098
2) 0.196
3) 0.294
4) 0.492

Correct Answer: 0.196

QID : 521 - Which of the following theorem explains the statement – ‘If the positions of voltage source and ammeter are interchanged with each other in a circuit, the reading of ammeter remains same and the circuit contains only 1 energy source.’?

1) Maximum power transfer theorem
2) Norton theorem
3) Reciprocity theorem
4) Superposition theorem

Correct Answer: Reciprocity theorem

QID : 522 -

1) 3.05
2) 3.15
3) 3.25
4) 3.35

Correct Answer: 3.35

QID : 523 - What will be the output (in Volts) of a voltage divider having resistance of 50 ohms and 150 ohms and a 20 V source when output is taken across 150 ohms resistor?

1) 15
2) 18
3) 20
4) 22

Correct Answer: 15

QID : 524 - Four resistors each of 5 kilo-ohms are connected in series with each other along with a 25 V voltage source. If a 20 kilo-ohms resistor is connected in parallel across one of the 5 kilo-ohms resistance, then what will be the value of total current (in mA) flowing in the circuit?

1) 0.654
2) 0.685
3) 0.893
4) 1.316

Correct Answer: 1.316

QID : 525 -

1) 2 A current source with 32 ohms resistor in parallel
2) 4 A current source with 16 ohms resistor in parallel
3) 2 A current source with 32 ohms resistor in series
4) 4 A current source with 16 ohms resistor in series

Correct Answer: 4 A current source with 16 ohms resistor in parallel

QID : 526 - What is the value of current (in A) at a point where 54 C of charge passes in 16 seconds?

1) 2.275
2) 3
3) 3.375
4) 4

Correct Answer: 3.375

QID : 527 - What is the capacitance (in µF) of a parallel plate capacitor if it stores 15 mC of charge when connected across 18 V supply?

1) 8.33
2) 16.66
3) 83.33
4) 833.33

Correct Answer: 833.33

QID : 528 - Which of the following uses wiper sliding contact?

1) Diode
2) LED
3) Potentiometer
4) Thermistor

Correct Answer: Potentiometer

QID : 529 - What is the voltage (in Volts) across a 5 H inductor when a current of (15 t + 30) A is flowing through the circuit?

1) 55
2) 60
3) 65
4) 75

Correct Answer: 75

QID : 530 - What is the admittance (in mho) of a circuit in which 5 ohms and 15 ohms series resistors are connected in series with an inductor having inductive reactance of 25 ohms?

1) 0.03125
2) 0.625
3) 1.25
4) 12.5

Correct Answer: 0.03125

QID : 531 - What is the value of susceptance (in Siemens) of a circuit if the same circuit has reactance and resistance of 8 ohms and 6 ohms respectively?

1) -0.08
2) -0.04
3) 0
4) 0.04

Correct Answer: -0.08

QID : 532 - What is the value of conductance (in Siemens) of a circuit if the same circuit has reactance and resistance of 8 ohms and 6 ohms respectively?

1) -0.06
2) -0.03
3) 0
4) 0.06

Correct Answer: 0.06

QID : 533 -

1) 20
2) 21
3) 25
4) 29

Correct Answer: 29

QID : 534 - What is the quality factor of a series RLC circuit having resistance, inductance and capacitance of 20 ohms, 1 mH and 0.01 mF, respectively?

1) 0.5
2) 0.75
3) 1
4) 1.25

Correct Answer: 0.5

QID : 535 - What is the quality factor of a parallel RLC circuit having resistance, inductance and capacitance of 20 ohms, 1 mH and 0.01 mF respectively?

1) 0.5
2) 1
3) 1.5
4) 2

Correct Answer: 2

QID : 536 - What is the bandwidth (in Hz) of a parallel RLC circuit having resistance, inductance and capacitance of 20 ohms, 1 mH and 0.01 mF respectively with a resonant frequency of 60 Hz?

1) 20
2) 30
3) 40
4) 50

Correct Answer: 30

QID : 537 - A delta connected network consumes 6.4 kW at 0.8 lagging power factor when connected to a 400 V, 50 Hz source. What is the approximate per phase impedance (in Ohms) of the delta network?

1) 50
2) 55
3) 60
4) 6

Correct Answer: 60

QID : 538 - A star connected load has phase current of 10 A and equal phase impedance of (4 + j3) ohms. Calculate the value of line voltage (in Volts) supplying the star connected load.

1) 64.4
2) 86.6
3) 108.8
4) 131

Correct Answer: 86.6

QID : 539 - If a delta network has three equal resistances each of 153 ohms, then, calculate the equivalent star network resistance (in Ohms) in each phase.

1) 51
2) 102
3) 153
4) 306

Correct Answer: 102

QID : 540 - What is the value of separation between the voltages in a balanced three-phase system?

1) 30°
2) 45°
3) 60°
4) 120°

Correct Answer: 120°

QID : 541 - What is the 16's compliment of hexadecimal number 5EF?

1) 9A0
2) 921
3) AF1
4) A11

Correct Answer: A11

QID : 542 - How many inputs are required to form truth table of the SOP expression ABD + BD + A + AD?

1) 1
2) 2
3) 3
4) 4

Correct Answer: 3

QID : 543 - What is minimum number of logic gates required to implement the Boolean expression AB + A (A + B) + B (A + B) without simplifying it?

1) 1
2) 2
3) 3
4) 5

Correct Answer: 5

QID : 544 - What is the resolution (in Volts) of a 4-bit ADC having reference voltage of 12 V?

1) 0.5
2) 0.75
3) 1
4) 1.25

Correct Answer: 0.75

QID : 545 - What will be the voltage reading of an ADC having resolution of 1023 and reference voltage of 5 V while measuring a voltage of 4.3 V?

1) 660
2) 770
3) 880
4) 990

Correct Answer: 880

QID : 546 - What is the output frequency (in kHz) of a frequency division circuit having 10 flip-flops with an input clock frequency of 40.96 MHz?

1) 10
2) 20
3) 30
4) 40

Correct Answer: 40

QID : 547 - What is the minimum number of flip-flops required to produce modulo-256 counter?

1) 1
2) 2
3) 4
4) 8

Correct Answer: 8

QID : 548 - What will be the count in a MOD-8 ripple counter which is holding the binary count 101 after 25 clock pulses?

1) 100
2) 101
3) 110
4) 010

Correct Answer: 110

QID : 549 - The group of bits 10101 is serially shifted (right-most bit first) into a 5-bit parallel output shift register with an initial state of 01001. What is the value contained in the register after 2 clock pulses?

1) {01010}
2) {01011}
3) {10001}
4) {10011}

Correct Answer: {01010}

QID : 550 - If the input resistor of 50 kilo-ohms of a binary weighted DAC is connected to a 6 V supply, then, what will be the current flowing through the resistor?

1) 60 µA
2) 120 µA
3) 6 mA
4) 60 mA

Correct Answer: 120 µA

Study Kit for SSC Scientific Assistant (IMD) Examination

QID : 551 - What is the expression for minimum transmission bandwidth of a PAM-TDM channel?

Correct Answer: 2

QID : 552 - Crosstalk is defined as _______________.

1) Interference between adjacent TDM channels
2) Interference between adjacent PCM channels
3) Interference between adjacent PAM channels
4) Interference between adjacent AM channels

Correct Answer: Interference between adjacent TDM channels

QID : 553 - The number of simultaneous conversations that can be transmitted using FDM depends on the total ______________ available.

1) Frequency components
2) Phase
3) Bandwidth
4) Both frequency and bandwidth

Correct Answer: Bandwidth

QID : 554 - Which of the following modulation technique is rare in digital communication?

1) FSK
2) PSK
3) ASK
4) BPSK

Correct Answer: ASK

QID : 555 - Which non-coherent binary modulation technique uses two transmitted frequencies in noisy channel?

1) FSK
2) BPSK
3) QPSK
4) ASK

Correct Answer: FSK

QID : 556 - Which modulation technique is preferred over amplitude shift keying (ASK)?

1) FSK
2) BPSK
3) MSK
4) FSK and PSK

Correct Answer: FSK and PSK

QID : 557 - What is the minimum bandwidth of a BPSK signal?

Correct Answer: 2

QID : 558 - On which factor, the probability of error of ASK modulation technique depends?

1) Amplitude
2) Signal energy
3) Bit rate
4) Error signal

Correct Answer: Signal energy

QID : 559 - What is the range of losses caused due to hydrogen absorption mechanisms?

1) 0 dB/km to 5 dB/km
2) 10 dB/km to 15 dB/km
3) 20 dB/km to 25 dB/km
4) 25 dB/km to 50 dB/km

Correct Answer: 25 dB/km to 50 dB/km

QID : 560 - Which among the following is/are correct with respect to PCM?

1. PCM system has better noise immunity as compared to other systems.
2. PCM is unaffected by width of the pulses.
3. PCM is affected by the position of the pulses.

1) 1 only
2) 1 and 2 only
3) 1 and 3 only
4) 2 and 3 only

Correct Answer: 1 and 2 only

QID : 561 - A binary PCM system transmits a TV signal having a bandwidth of 3.2 MHz with 512 number of quantization levels. Calculate the code word length and transmission bandwidth of given PCM system respectively.

1) 5 bits, 35 MHz
2) 6 bits, 27.5 MHz
3) 9 bits, 28.8 MHz
4) 10 bits, 38.7 MHz

Correct Answer: 9 bits, 28.8 MHz

QID : 562 - In delta modulation, Granular or Idle noise occurs when step size is ___________ compared to small variations in the input signal.

1) Too large
2) Large
3) Small
4) Slightly less

Correct Answer: Too large

QID : 563 - The spectral efficiencies for all the line codes can be easily evaluated from their ______________.

1) Probability of error
2) Bandwidth
3) Power spectral density
4) Both Bandwidth and Power spectral density

Correct Answer: Power spectral density

QID : 564 - Determine the number of bits of quantization noise that are needed to achieve a signal to noise ratio of at least 40 dB?

1) 5 bits
2) 6 bits
3) 7 bits
4) 8 bits

Correct Answer: 7 bits

QID : 565 - Calculate the bandwidth of a PCM system, if the amplitude levels are transmitted in a 7 unit code and sampling is done at the rate of 10 kHz.

1) 25 kHz
2) 30 kHz
3) 35 kHz
4) 40 kHz

Correct Answer: 35 kHz

QID : 566 - Which of the following technique is not suitable for automatic satellite tracking?

1) Step-track technique
2) Conical scanning
3) Lobe switching
4) Mono pulse switching

Correct Answer: Step-track technique

QID : 567 - NASA launched three satellites, named Biosatellite (1, 2 & 3) between _______ and ________.

1) 1965, 1969
2) 1966, 1968
3) 1956, 1958
4) 1966, 1969

Correct Answer: 1966, 1969

QID : 568 - Which of the following contracted the launch of AsiaSat 2 satellite?

1) Asia Satellite Telecommunications Company (ASTC)
2) Japan Satellite System (JSAT)
3) China Great Wall Industry Corporation
4) Singapore Satellite Commission

Correct Answer: China Great Wall Industry Corporation

QID : 569 - The point on the satellite orbits that is close to the earth is ____________.

1) Apogee
2) Perigee
3) Prograde
4) Zenith

Correct Answer: Perigee

QID : 570 - Which of the following device is used for the conversion of electrons to photons or photons to electrons?

1) Antenna
2) Electron gun
3) Photon amplifier
4) Microwave tube

Correct Answer: Antenna

QID : 571 - What is the total number of radiation pattern required to specify the characteristics of an antenna?

1) One
2) Two
3) Three
4) Five

Correct Answer: Three

QID : 572 -

1) 10 dB
2) 11 dB
3) 12 dB
4) 13 dB

Correct Answer: 13 dB

QID : 573 - What is the directivity of an antenna that radiates power over half a sphere?

1) One
2) Two
3) Three
4) Four

Correct Answer: Two

QID : 574 - Determine the efficiency of an antenna (per cent), if the power at input side is 200 mW and the radiated power is to be 80 mW.

1) 0.5
2) 0.4
3) 0.355
4) 0.45

Correct Answer: 0.4

QID : 575 - In ________________ the media of transmission is a pair of conductors called transmission line.

1) Radio communication
2) Wireless communication
3) Line communication
4) Wired communication

Correct Answer: Line communication

QID : 576 - Which among the following is/are correct for the need of modulation?

1. Multiplexing
2. Narrow banding
3. Practicability of antennas

1) 1 only
2) 2 and 3 only
3) 1 and 3 only
4) 1, 2 and 3

Correct Answer: 1, 2 and 3

QID : 577 - A __________________ requires a non-linear element and a low pass filter for extracting the desired message signal.

1) Envelope detector
2) Square law detector
3) Demodulator
4) Frequency limiter

Correct Answer: Square law detector

QID : 578 - A compromise between the DSB-SC modulation and the SSB modulation is known as ____________.

1) VSB modulation
2) Conventional AM-DSB modulation
3) Angle modulation
4) Phase modulation

Correct Answer: VSB modulation

QID : 579 - Which of the following factor measures the performance of both Analog and digital communication system?

1) Input signal-to-noise power ratio
2) Output signal-to-noise power ratio
3) Probability of error
4) Both probability of error and output signal to noise power ratio

Correct Answer: Both probability of error and output signal to noise power ratio

QID : 580 - The demodulator filter which is the inverse of the modulator filter is called the _____________.

1) Pre-emphasis filter (HPF)
2) De-emphasis filter (LPF)
3) Band pass filter
4) Demodulation filter

Correct Answer: De-emphasis filter (LPF)

QID : 581 - Which of the following shift keying involved the most complex signal detection process?

1) ASK
2) FSK
3) PSK
4) Both ASK and FSK

Correct Answer: PSK

QID : 582 - Delta modulation transmits ___________ per sample.

1) one bit
2) two bytes
3) three bytes
4) four bytes

Correct Answer: three bytes

QID : 583 - What is the meaning of scrambling of data?

1) Exchanging of data
2) Removing long strings of 1's and 0's
3) Transmission of digital data
4) Transmission of Analog data

Correct Answer: Removing long strings of 1's and 0's

QID : 584 - Which of the following is the correct sequence of subsystems in an FM receiver?

1) Mixer, RF amplifier, Limiter, IF amplifier, Discriminator, Audio amplifier
2) RF amplifier, Mixer, Limiter, IF amplifier, Discriminator, Audio amplifier
3) Mixer, RF amplifier, IF amplifier, Limiter, Discriminator, Audio amplifier
4) Mixer, RF amplifier, Limiter, Discriminator, IF amplifier, Audio amplifier

Correct Answer: RF amplifier, Mixer, Limiter, IF amplifier, Discriminator, Audio amplifier

QID : 585 - In frequency modulation, the frequency deviation is _________________ to the modulating signal frequency.

1) directly proportional
2) inversely proportional
3) independent
4) inversely proportional to the square root of modulating signal

Correct Answer: directly proportional

QID : 586 - Determine the value of power in the carrier of modulation index of 0.5, if the radiated power of AM transmitter is 10 kW.

1) 13 kW
2) 13.33 kW
3) 14.45 kW
4) 15 kW

Correct Answer: 14.45 kW

QID : 587 - Which of the following noise affects the performance of communication system at higher frequencies?

1) Shot noise
2) Flicker noise
3) Random noise
4) Transit-time noise

Correct Answer: Transit-time noise

QID : 588 - To get FM by using PM, we first ____________ the baseband signal and then apply to the phase modulation.

1) Differentiate
2) Integrate
3) Multiply
4) Limit

Correct Answer: Integrate

QID : 589 - The artificial boosting of higher modulating frequencies is called ______________.

1) Pre-emphasis
2) De-emphasis
3) Frequency limiting
4) Amplitude limiting

Correct Answer: Pre-emphasis

QID : 590 -

1) 67.5 kHz, 83.5 %
2) 62.5 kHz, 83.3%
3) 60.25 kHz, 90.4 %
4) 66.7 kHz, 85.3%

Correct Answer: 62.5 kHz, 83.3%

QID : 591 - Which of the following propagation is also termed as point-to-point propagation?

1) Ground wave propagation
2) Space wave propagation
3) Sky wave propagation
4) Troposphere scatter propagation

Correct Answer: Sky wave propagation

QID : 592 - Which of the following is the line of sight (LOS) propagation?

1) Forward scatter propagation
2) Backward scatter propagation
3) Space wave propagation
4) Duct propagation

Correct Answer: Space wave propagation

QID : 593 -

1) 12.727 MHz
2) 15.525 MHz
3) 17.772 MHz
4) 14.386 MHz

Correct Answer: 12.727 MHz

QID : 594 - The phenomenon of splitting of wave into two different components by the earth's magnetic field is termed as ___________________.

1) Magnet splitting
2) Magnet ionic splitting
3) Magneto ionic splitting
4) Magneto splitting

Correct Answer: Magneto ionic splitting

QID : 595 - Which of the following Ionospheric abnormalities is also termed as Mongel-Dellinger Effect?

1) Ionospheric storms
2) Sun spot cycle
3) Fadings
4) Sudden ionospheric disturbances (SID)

Correct Answer: Sudden ionospheric disturbances (SID)

QID : 596 - Which type of signals is propagating primarily by ground waves during the day and by sky waves at night?

1) FM broadcast signals
2) AM broadcast signals
3) Sinusoidal signals
4) Both AM and FM signals

Correct Answer: AM broadcast signals

QID : 597 - The carrier amplitude after AM varies between 5 volts and 2 volts. Determine the depth of modulation.

1) 0.45
2) 0.425
3) 0.443
4) 0.5

Correct Answer: 0.425

QID : 598 - Which type of modulation produces the best type of amplitude modulation (AM)?

1) High level modulation
2) Low level modulation
3) Mid level modulation
4) Both High level modulation and Low level modulation

Correct Answer: High level modulation

QID : 599 - What are the frequency components in an AM wave?

Correct Answer: 4

QID : 600 - Calculate the peak amplitude of the carrier of an antenna of (50 + j 0) ohms load if given AM broadcast station transmits a total power of 50 kW and its carrier power is 40 kW.

1) 53 kV
2) 63.24 kV
3) 64 kV
4) 65 kV

Correct Answer: 63.24 kV