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Power in ac

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  • Which formula correctly represents true power using RMS values?
    P = VRMS × IRMS
  • In resistive circuits, power is always:
    •   Positive
  • Why does a pure inductor not dissipate power as heat?
    Because an ideal inductor stores energy in its magnetic field and returns it to the source
  • What unit is used to measure reactive power?
    VAR (Volt-Amps Reactive)
  • How is instantaneous power calculated in AC circuits?
    p(t) = v(t) × i(t)
  • What is the average true power in a purely inductive AC circuit?
    Zero
  • How does the frequency affect inductive reactance?
    It increases — XL is proportional to frequency.
  • In a capacitive circuit, current leads or lags voltage?
    Lead
  • What is the formula for calculating reactive power using current and reactance?
    Q = I² × X (or Q = V² / X
  • What type of power is associated with energy returned to the source?
    Reactive Power
  • What does a power factor of 1 indicate about a circuit?
    That all the power is being used effectively — no reactive component
  • Which type of component alternately stores and returns energy in the form of a magnetic field?
    Inductor
  • Define ‘apparent power’ and state its unit.
    Apparent power is the vector sum of true and reactive power, measured in VA (Volt-Amps).
  • What is the formula for capacitive reactance (XC)?
    XC = 1 / (2πfC)
  • Explain why the power waveform in AC circuits has twice the frequency of voltage/current.
    Because both current and voltage are sinusoidal and their product results in a sine-squared waveform.
  • In an inductive circuit, does current lead or lag voltage?
    Lag
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