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AC Circuit Analysis & Power Flashcards

7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 AC Circuit Analysis & Power flashcards as text

  1. In a series RLC circuit at resonance, which statement is TRUE?

    Answer: Inductive and capacitive reactances are equal and cancel

    At resonance, XL = XC, so they cancel, leaving only resistance in the circuit.

  2. What is the phase relationship between voltage and current in a purely capacitive AC circuit?

    Answer: Current leads voltage by 90°

    In a purely capacitive circuit, current leads voltage by 90° (ELI the ICE man mnemonic — I before E in C).

  3. A circuit has a true power of 300 W and an apparent power of 500 VA. What is the reactive power?

    Answer: 400 VAR

    Reactive power Q = √(S² − P²) = √(500² − 300²) = √(250000 − 90000) = √160000 = 400 VAR.

  4. Which instrument is used to measure the phase angle between voltage and current in an AC circuit?

    Answer: Power factor meter

    A power factor meter directly measures the cosine of the phase angle (power factor) between voltage and current.

  5. What happens to the capacitive reactance (XC) of a capacitor if the frequency of the applied AC signal is doubled?

    Answer: XC is halved

    Since XC = 1/(2πfC), doubling frequency halves the capacitive reactance.

  6. In an AC circuit, what does the Q factor (quality factor) of a resonant circuit indicate?

    Answer: The bandwidth relative to the resonant frequency

    The Q factor equals the resonant frequency divided by the bandwidth, indicating how selective (sharp) the resonance is.

  7. What is the impedance of a series circuit containing a 40 Ω resistor, XL = 80 Ω, and XC = 50 Ω?

    Answer: 50 Ω

    Z = √(R² + (XL − XC)²) = √(40² + 30²) = √(1600 + 900) = √2500 = 50 Ω.