Railways NTPC (Technical Ability) Basic Electronics Question Bank

done Basic Electronics Total Questions - 60

• question_answer1)
  An ideal diode
  A)
  should have zero resistance in the forward bias and zero resistance in the reverse bias done clear
  B)
  should have infinite large resistance in the reverse bias done clear
  C)
  should have zero resistance in the forward bias and an infinitely large resistance in the reverse bias done clear
  D)
  none of these done clear
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• question_answer2)
  Vacuum tubes in a radio transmitter are used to
  A)
  record programmes done clear
  B)
  d. c. supply done clear
  C)
  generate high power radio waves done clear
  D)
  none of these done clear
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• question_answer3)
  Which of the following electron emission process is widely used vacuum tubes?
  A)
  Thermionic emission        done clear
  B)
  Secondary emission done clear
  C)
  Photoelectric emission      done clear
  D)
  None of these done clear
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• question_answer4)
  Which of the following semiconductors has the highest melting point?
  A)
  Gallium arsenide done clear
  B)
  Germanium done clear
  C)
  Silicon   done clear
  D)
  None of these done clear
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• question_answer5)
  Power diodes are generally
  A)
  germanium diodes           done clear
  B)
  silicon diodes done clear
  C)
  I both [a] and [b]            done clear
  D)
  none of these done clear
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• question_answer6)
  In PN junction, the region containing the uncompensated receptor and donor ions is called
  A)
  active region                   done clear
  B)
  natural region done clear
  C)
  both [a] and [b] done clear
  D)
  depletion region done clear
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• question_answer7)
  The photoelectric current in amperes per watt of incident light depends upon
  A)
  intensity of incident light done clear
  B)
  frequency of incident light done clear
  C)
  both [a] and [b] done clear
  D)
  none of these done clear
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• question_answer8)
  In case of semiconductors, recombination is
  A)
  merging of two or more holes done clear
  B)
  merging of an just emerged electron with resulting hole in the semi-conductor done clear
  C)
  both [a] and [b] done clear
  D)
  none of the above done clear
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• question_answer9)
  Vacuum diode is a two-electrode vacuum tube, first is called cathode and the second is called
  A)
  symbol              done clear
  B)
  rectifier done clear
  C)
  anode    done clear
  D)
  none of these done clear
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• question_answer10)
  Which of the following emitter material usually needs less than 1000V as plate voltage?
  A)
  Pure tungsten     done clear
  B)
  Oxide coated done clear
  C)
  Both [a] and [b] done clear
  D)
  None of these done clear
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• question_answer11)
  In a diode the plate current increases when the
  A)
  saturation plate current is reached done clear
  B)
  plate voltage is made more positive done clear
  C)
  plate voltage is made less positive done clear
  D)
  none of these done clear
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• question_answer12)
  The maximum charge carried by an ion is
  A)
  equal to the charge of number of electrons gained or lost by the atom on ionization done clear
  B)
  zero done clear
  C)
  equal to the charge of electrons left in the atom done clear
  D)
  none of these done clear
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• question_answer13)
  The forbidden energy gap in semiconductors
  A)
  lies between the valence band and the conduction band done clear
  B)
  lies above the conduction band done clear
  C)
  is always zero done clear
  D)
  none of these done clear
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• question_answer14)
  For a PN junction diode, the current in reverse bias may be
  A)
  few micro or nano amperes done clear
  B)
  few amperes done clear
  C)
  between 0.25 and 1A done clear
  D)
  none of these done clear
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• question_answer15)
  For d. c. power supply, diode can be used as a detector and a
  A)
  emitter               done clear
  B)
  rectifier done clear
  C)
  either [a] and [b] done clear
  D)
  none of these done clear
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• question_answer16)
  The bulk resistance of a diode is
  A)
  the resistance of P and N materials done clear
  B)
  the resistance of junction only done clear
  C)
  the resistance of P material only done clear
  D)
  the resistance of N material only done clear
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• question_answer17)
  The emission of electrons in a vacuum diode is achieved by
  A)
  heating  done clear
  B)
  magnetic field done clear
  C)
  electric field                    done clear
  D)
  none of these done clear
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• question_answer18)
  A fall were bridge rectifier is supplied voltage at 50Hz. The lowest ripple frequency will be
  A)
  100 Hz  done clear
  B)
  95 Hz done clear
  C)
  75 Hz                done clear
  D)
  225 Hz done clear
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• question_answer19)
  Which of the following results in the movement of a hole?
  A)
  A vacancy is filled by a valence electron from the neighbouring atom done clear
  B)
  Moment of protons done clear
  C)
  Moment of neutrons done clear
  D)
  None of the above done clear
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• question_answer20)
  For vacuum tubes the negative grid voltage of smallest magnitude required to make the plate current zero is called:
  A)
  Cut-off grid voltage         done clear
  B)
  Minimum grid voltage done clear
  C)
  Both [a] and [b] done clear
  D)
  None of these done clear
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• question_answer21)
  When the cathode of vacuum tube is heated and anode is not connected to any external circuit
  A)
  electrons form a space charge done clear
  B)
  protons are emitted from anode done clear
  C)
  glass tube gets charged done clear
  D)
  none of these done clear
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• question_answer22)
  Oxide coated cathodes are used for the tubes
  A)
  used in radio transmitters done clear
  B)
  Power Rectifiers done clear
  C)
  designed to handle small power done clear
  D)
  none of the above done clear
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• question_answer23)
  The maximum forward current in case of low power signal diode is in the range of  
  A)
  few milli-amperes            done clear
  B)
  0.1A to 0.5A done clear
  C)
  1 A to 2.5A                    done clear
  D)
  1.25A to 3.25A done clear
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• question_answer24)
  When PN junction is in forward bias, by increasing the battery voltage
  A)
  current through PN junction increases done clear
  B)
  circuit resistance increases done clear
  C)
  both [a] and [b] done clear
  D)
  none of these done clear
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• question_answer25)
  The principle of emission of electrons from a metal surface, under the influence of light is known as
  A)
  secondary emission         done clear
  B)
  photoelectric emission done clear
  C)
  thermionic emission   done clear
  D)
  none of these done clear
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• question_answer26)
  The bandwidth of a difference amplifier is comparable to that of a
  A)
  single-stage CE amplifier done clear
  B)
  double-stage CE amplifier done clear
  C)
  cascade amplifier done clear
  D)
  Darlington amplifier done clear
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• question_answer27)
  Which of the following transistors can be used in enhancement mode?
  A)
  UJT                              done clear
  B)
  JFET done clear
  C)
  MOSFET           done clear
  D)
  NPN transistor done clear
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• question_answer28)
  Zener diodes                                     
  A)
  have breakdown voltage of less than 5V and have ve temperature coefficient                     done clear
  B)
  have breakdown voltage of less than 5V and have                                                                                   \[a+ve\] temperature coefficient                     done clear
  C)
  have breakdown voltage of more than 5V and have                                                                                   \[a+ve\] temperature coefficient                     done clear
  D)
  have breakdown voltage of 5 V and have a  temperature coefficient   done clear
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• question_answer29)
                      In a semiconductor, the movement of holes is due to
  A)
  movement of electrons in conduction band      done clear
  B)
  movement of holes in conduction band          done clear
  C)
  movement of holes in valence band             done clear
  D)
  movement of electrons in valence band          done clear
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• question_answer30)
  In a CE transistor amplifier, if collector?emitter increases, the instantaneous operating point         
  A)
  moves up the load line                         done clear
  B)
  moves down the load line                    done clear
  C)
  moves at right angles to the load line             done clear
  D)
  remains stationary   done clear
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• question_answer31)
                             When a P?N junction is forward biased            
  A)
  the width of the depletion layer is decreased      done clear
  B)
  the width of depletion layer is increased          done clear
  C)
  the width of the depletion layer remains the same done clear
  D)
  none of these done clear
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• question_answer32)
                                 One disadvantage of directly coupled transistor amplifier
  A)
  identical transistors are required                   done clear
  B)
  both NPN transistors are required              done clear
  C)
  variations in current due to temperature changes  one stage are amplified by other stages               done clear
  D)
  the low frequency response is poor     done clear
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• question_answer33)
           A UJT has                                       
  A)
  stable negative resistance characteristics      done clear
  B)
  low firing current                               done clear
  C)
  use as a waveform generator                   done clear
  D)
  all of these characteristics     done clear
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• question_answer34)
                      In a properly biased transistor                       
  A)
  both depletion regions are large                  done clear
  B)
  both depletion regions are small                 done clear
  C)
  the emitter to base depletion region is small collector to base depletion region is large        done clear
  D)
  the emitter to base depletion region is large an collector to base depletion region is small     done clear
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• question_answer35)
       Dynamic resistance is the ratio of                  
  A)
  change in drain-source voltage and change in drain current at constant                                                                             \[{{V}_{GS}}\] done clear
  B)
  change in gate-source voltage and change in drain current at constant                                                                             \[{{V}_{DS}}\]   done clear
  C)
  Drain-source voltage and drain current done clear
  D)
  gate-source voltage and drain current done clear
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• question_answer36)
  The ratio of diffusion constant for electrons                                                                              \[{{D}_{E}}\] to the mobility for electrons                                                                            \[{{\mu }_{e}}\] is
  A)
  independent of T done clear
  B)
  inversely proportional to T done clear
  C)
  proportional to                                                                              \[{{T}^{2}}\] done clear
  D)
  proportional to T done clear
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• question_answer37)
  The addition of trivalent impurity to an intrinsic semiconductor creates
  A)
  N-type semiconductor done clear
  B)
  excess free electrons done clear
  C)
  excess holes          done clear
  D)
  electron-hole pairs   done clear
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• question_answer38)
  In a fall wave rectifier circuit the peak inverse voltage per diode is
  A)
  the same as that in a half wave circuit done clear
  B)
  half the value in a half wave circuit done clear
  C)
  double the value in a half wave circuit done clear
  D)
  none of above done clear
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• question_answer39)
  The potential barrier acts as a barrier against the flow of
  A)
  electrons only     done clear
  B)
  holes only done clear
  C)
   electrons and holes         done clear
  D)
  None of these done clear
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• question_answer40)
  The number of valence electron in boron is
  A)
  1                                  done clear
  B)
  2 done clear
  C)
  3                      done clear
  D)
  5 done clear
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• question_answer41)
  When an electron breaks a covalent bond and moves away
  A)
  the semiconductor becomes conductor done clear
  B)
  a valency is created in broken covalent bond done clear
  C)
  the conductivity of the material increase done clear
  D)
  more ions are produced done clear
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• question_answer42)
  The conduction band is
  A)
  the region of free electrons done clear
  B)
  a range of energies corresponding to the energies of the free electrons done clear
  C)
  always above the forbidden energy level done clear
  D)
  concentrated holes for the flow of current done clear
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• question_answer43)
  The merging of a free electron and a hole is known as
  A)
  recombination    done clear
  B)
  extrusion done clear
  C)
  absorption                      done clear
  D)
  adsorption done clear
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• question_answer44)
  The majority charge carriers in an n-type semiconductors are
  A)
  holes                 done clear
  B)
  electrons done clear
  C)
  neutrons            done clear
  D)
  None of these done clear
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• question_answer45)
  Which of the following are immobile?
  A)
  Electrons                        done clear
  B)
  Holes done clear
  C)
  Ions                  done clear
  D)
  None of these done clear
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• question_answer46)
  The transferred-electron bulk effect occurs in
  A)
   silicon done clear
  B)
  germanium done clear
  C)
   gallium done clear
  D)
  metal semiconductor junction done clear
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• question_answer47)
  What type of electron carriers in n-type semiconductor?
  A)
  Minority             done clear
  B)
  Majority done clear
  C)
  Both [a] and [b] done clear
  D)
  None of these done clear
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• question_answer48)
  Which of the following has the highest mobility?
  A)
  Neutron             done clear
  B)
  Electron done clear
  C)
  Positive ions                   done clear
  D)
  Negative ions done clear
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• question_answer49)
  In p-n junction with no external voltage, the electric field between the acceptor and the donor ions is called a
  A)
  barrier   done clear
  B)
  threshold done clear
  C)
  peak                              done clear
  D)
  path done clear
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• question_answer50)
  In a p-n junction the potential barrier is due to the charges on either side of the junction. These charges are
  A)
  majority carriers done clear
  B)
  minority carriers done clear
  C)
  both majority as well as minority carriers done clear
  D)
  fixed donor and acceptor ions done clear
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• question_answer51)
  In a p-n-p transistor
  A)
   the electrons are the minority carriers in the base region done clear
  B)
  the base is made by doping the intrinsic semiconductor with indium done clear
  C)
  the emitter injects holes into the base region done clear
  D)
  the principal current carriers are electrons done clear
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• question_answer52)
  In the symbol of a                                                                                   \[p-n-p\] or                                                                                   \[n-p-n\] transistor, the lead marked with an arrow is
  A)
  the collector lead done clear
  B)
  the emitter lead done clear
  C)
  the base lead                  done clear
  D)
  the earthling lead done clear
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• question_answer53)
  The p-n junction behaves like a
  A)
  pentode             done clear
  B)
  tetrode done clear
  C)
  triode                done clear
  D)
  diode done clear
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• question_answer54)
  The process of adding impurities to a semiconductor is known as
  A)
  polling               done clear
  B)
  intrusion done clear
  C)
  pugging              done clear
  D)
  doping done clear
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• question_answer55)
  The semiconductor diode can be used for
  A)
  half wave rectifiers          done clear
  B)
  full wave rectifiers done clear
  C)
  both [a] and [b]  done clear
  D)
  None of these done clear
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• question_answer56)
  The number of diodes required in a bridge rectifier circuit is
  A)
  one                               done clear
  B)
  two done clear
  C)
  three                             done clear
  D)
  four done clear
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• question_answer57)
  A transistor is a combination of two p-n junction with their
  A)
  p region connected together done clear
  B)
  n region connected together done clear
  C)
  n region connected to other p region done clear
  D)
  [a] and [b] done clear
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• question_answer58)
  Which of the following diode will produce the highest pulsed power output?
  A)
  Varactor                        done clear
  B)
  Gunn done clear
  C)
  RIMPATT                      done clear
  D)
  Schottky barrier done clear
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• question_answer59)
  In triode valve, the plate of characteristic plotted with positive and negative grid voltages will have
  A)
   different slopes done clear
  B)
  almost same slopes done clear
  C)
  positive and negative slopes respectively done clear
  D)
  none of the above done clear
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• question_answer60)
  Which of the following is a unipolar diode?
  A)
  Zener diode                    done clear
  B)
  Step recovery diode done clear
  C)
  Schottky diode   done clear
  D)
  All of these done clear
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