Alternating Current

Q1.In a series LCR circuit with R = 3 Ω, XL = 8 Ω, and XC = 4 Ω, the impedance of the circuit is:

• A9 Ω
• B5 Ω
• C15 Ω
• D3 Ω

Q2.In a purely resistive AC circuit, the phase relationship between voltage and current is:

• ACurrent leads voltage by π/2
• BVoltage leads current by π/2
• CVoltage and current are in phase
• DCurrent lags voltage by π/4

Q3.The average power dissipated in an AC circuit is given by P = VI cos φ. If the rms voltage is 100 V, rms current is 2 A, and phase angle is 60°, the average power is:

• A200 W
• B100 W
• C173 W
• D86.6 W

Q4.The Q-factor (quality factor) of a series RLC circuit is defined as ω₀L/R. For a circuit with L = 1 mH, C = 1 nF, and R = 100 Ω, the Q-factor is:

• A1
• B5
• C10
• D100

Q5.A 25 mH pure inductor is connected to a 220 V, 50 Hz source. What is the rms current in the circuit?

• A14 A
• B28 A
• C7.85 A
• D56 A