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
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.
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).
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.
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.
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.
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.
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.