Silicon Controlled Rectifiers MCQ

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• An SCR combines the features of ___________
  ক

  A rectifier and resistance

  খ

  A rectifier and transistor

  গ

  A rectifier and capacitor

  ঘ

  None of the above
• An SCR has ___________ semiconductor layers
  ক

  Two

  খ

  Three

  গ

  Four

  ঘ

  None of the above
• An SCR is sometimes called ___________
  ক

  Triac

  খ

  Diac

  গ

  Unijunction transistor

  ঘ

  Thyristor
• When SCR is OFF, the current in the circuit is ___________
  ক

  Exactly zero

  খ

  Small leakage current

  গ

  Large leakage current

  ঘ

  None of the above
• If gate current is increased, then anode-cathode voltage at which SCR closes ___________
  ক

  Is decreased

  খ

  Is increased

  গ

  Remains the same

  ঘ

  None of the above
• An SCR is turned off when ___________
  ক

  Anode current is reduced to zero

  খ

  Gate voltage is reduced to zero

  গ

  Gate is reverse biased

  ঘ

  None of the above
• In an SCR circuit the supply voltage is generally ___________ that of breakover voltage
  ক

  Equal to

  খ

  Less than

  গ

  Greater than

  ঘ

  None of the above
• We can control a.c. power in a load by connecting ___________
  ক

  Two SCRs in series

  খ

  Two SCRs in parallel

  গ

  Two SCRs in parallel opposition

  ঘ

  None of the above
• An SCR is made of silicon and not germanium because silicon
  ক

  Is inexpensive

  খ

  Is mechanically strong

  গ

  Has small leakage current

  ঘ

  Is tetravalent
• An SCR has three terminals viz ___________
  ক

  Cathode, anode, gate

  খ

  Anode, cathode, grid

  গ

  Anode, cathode, drain

  ঘ

  None of the above
• The control element of an SCR is ___________
  ক

  Cathode

  খ

  Anode

  গ

  Anode supply

  ঘ

  Gate
• When an SCR is turned on, the voltage across it is about ___________
  ক

  Zero

  খ

  10 V

  গ

  1.5 V

  ঘ

  1 V
• If firing angle in an SCR circuit is increased, the output ___________
  ক

  Remains the same

  খ

  Is increased

  গ

  Is decreased

  ঘ

  None of the above
• An SCR is turned off by ___________
  ক

  Reducing anode voltage to zero

  খ

  Reducing gate voltage to zero

  গ

  Reverse biasing the gate

  ঘ

  None of the above
• The normal way to turn on a SCR is by ___________
  ক

  Breakover voltage

  খ

  Appropriate anode current

  গ

  Appropriate gate current

  ঘ

  None of the above
• In an SCR circuit, the angle of conduction can be changed by ___________
  ক

  Changing anode voltage

  খ

  Changing gate voltage

  গ

  Reverse biasing the gate

  ঘ

  None of the above
• An SCR is a solid state equivalent of ___________
  ক

  Triode

  খ

  Pentode

  গ

  Gas-filled triode

  ঘ

  Tetrode
• An SCR behaves as a ___________ switch
  ক

  Unidirectional

  খ

  Bidirectional

  গ

  Mechanical

  ঘ

  None of the above
• In normal operation of an SCR, gate is ___________w.r.t. cathode
  ক

  Positive

  খ

  Negative

  গ

  At zero potential

  ঘ

  None of the above
• An SCR has ___________ pn junctions
  ক

  Two

  খ

  Three

  গ

  Four

  ঘ

  None of the above
• In the normal operation of an SCR, anode is ___________ w.r.t. cathode
  ক

  At zero potential

  খ

  Negative

  গ

  Positive

  ঘ

  None of the above
• An SCR can exercise control over ___________ of a.c. supply
  ক

  Positive half-cycles only

  খ

  Negative half-cycles only

  গ

  Both positive and negative half-cycles

  ঘ

  Positive or negative half-cycles
• An SCR is a ___________ triggered device
  ক

  Voltage

  খ

  Current

  গ

  Voltage as well as current

  ঘ

  None of the above
• When SCR starts conducting, then ___________ loses all control
  ক

  Gate

  খ

  Cathode

  গ

  Anode

  ঘ

  None of the above
• An SCR is made of ___________
  ক

  Germanium

  খ

  Silicon

  গ

  Carbon

  ঘ

  None of the above