NCERT/Class 12/Physics/Alternating Current

Alternating Current

Class 12 · Physics

40 questions14 easy14 medium12 hard

Sample Questions

Q1.In a series LCR circuit, if XC > XL, the phase angle φ between voltage and current is:

  • APositive; current lags voltage
  • BNegative; current lags voltage
  • CPositive; current leads voltage
  • DZero; voltage and current are in phase

Q2.The phase angle in a series RLC circuit is φ = tan⁻¹((XC – XL)/R). If XL = 10 Ω, XC = 4 Ω, and R = 6 Ω, the magnitude of the phase angle is:

  • A30°
  • B45°
  • C53.1°
  • D60°

Q3.In a transformer, the energy loss due to hysteresis occurs because:

  • AThe windings have electrical resistance
  • BNot all flux links both coils
  • CThe alternating magnetic field repeatedly reverses the magnetisation of the iron core
  • DEddy currents flow in the windings

Q4.Wattless current refers to the component of current that:

  • ADissipates maximum power in the circuit
  • BIs in phase with the applied voltage
  • CIs perpendicular to the applied voltage and dissipates no power
  • DFlows only in resistors

Q5.In transmission of electrical energy over long distances, transformers are used primarily to:

  • AIncrease the current for efficient transmission
  • BStep up the voltage (and reduce current) to minimise I²R losses
  • CConvert AC to DC for long-distance transmission
  • DIncrease the power of the generator

Q6.This is a sample question to preview what you'll get in the full practice test...

  • A. Option one
  • B. Option two
  • C. Option three
  • D. Option four
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Concepts Covered

AC Voltage and CurrentCapacitive ReactanceImpedanceInductive ReactancePhasorsPower FactorPower TransmissionRMS ValuesResonanceSeries LCR CircuitTransformersWattless Current

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