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NTPC MCQs

Practice questions are arranged in pages of up to 100 MCQs.

Question 1
Analog ElectronicsOperational Amplifiers

For an ideal operational amplifier, the input impedance is assumed to be?

  • AZero
  • BInfinite
  • C1 ohm
  • DEqual to output impedance
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Correct Answer: B. Infinite
Explanation: An ideal op-amp draws zero input current; therefore its input impedance is considered infinite.
Reference: Ideal operational amplifier characteristics
Question 2
Network TheoryCircuit Laws

Kirchhoff’s Current Law is based on conservation of?

  • AEnergy
  • BCharge
  • CPower
  • DMomentum
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Correct Answer: B. Charge
Explanation: KCL follows conservation of electric charge: the algebraic sum of currents at a node is zero.
Reference: Kirchhoff's circuit laws
Question 3
Power ElectronicsPower Semiconductor Devices

Which device is commonly used as a controlled switch in power-electronic circuits?

  • ASCR
  • BLDR
  • CZener diode only
  • DPhotodiode
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Correct Answer: A. SCR
Explanation: An SCR is a thyristor widely used as a controlled switching device in power-electronic converters.
Reference: Power electronics fundamentals
Question 4
Control SystemsStability

For a stable continuous-time linear system, poles of the closed-loop transfer function should generally lie in which region of the s-plane?

  • ARight half-plane
  • BLeft half-plane
  • COnly on the imaginary axis
  • DAt the origin only
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Correct Answer: B. Left half-plane
Explanation: For an asymptotically stable continuous-time LTI closed-loop system, its poles lie in the left half of the s-plane.
Reference: Classical control-system stability criterion