AC Circuits and Power Factor MCQs 2026

38 questions with detailed answers · 28 from past papers · 4 quiz batches available

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Read each question, think about the answer, then click Show Answer to reveal the correct option and explanation. Load 10 at a time so it stays manageable — perfect for one-topic study sessions on the bus or during a break.

Page 1 of 1Questions 1–10 of 38

Q1Past Paper · PPSC/FPSC/CSSmedium
Phase angle for R-C series circuit is
1. Atan inverse (XC/R) leading
2. Btan inverse (R/XC) lagging
3. Czero always
4. D180 degrees
💡 Explanation:
Current leads voltage in RC.
Q2Past Paper · PPSC/FPSC/CSSmedium
An R-C series circuit has impedance
1. AR plus XC always
2. BR minus XC
3. CXC only
4. Dsqrt(R squared + XC squared)
💡 Explanation:
Z = sqrt(R² + XC²).
Q3medium
If P=100 W and phi=45 deg with same V I, power factor is
1. A0.29
2. B0.707
3. C1.41
4. D0.71
💡 Explanation:
PF = cos 45 = 0.707.
Q4medium
XC at f=60 Hz, C=0.00008 F is approximately
1. A33.2 ohm
2. B332 ohm
3. C3.32 ohm
4. D0.332 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 33.2 ohm.
Q5Past Paper · PPSC/FPSC/CSSmedium
XC at f=50 Hz, C=0.0002 F is approximately
1. A15.9 ohm
2. B159 ohm
3. C1.59 ohm
4. D0.159 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 15.9 ohm.
Q6Past Paper · PPSC/FPSC/CSSmedium
XC at f=100 Hz, C=0.00001 F is approximately
1. A1590 ohm
2. B15.9 ohm
3. C1.59 ohm
4. D159 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 159 ohm.
Q7medium
R=3 ohm, X=4 ohm in series: |Z| is
1. A7 ohm
2. B5 ohm
3. C1 ohm
4. D12 ohm
💡 Explanation:
|Z| = sqrt(3²+4²) = 5 ohm.
Q8Past Paper · PPSC/FPSC/CSSmedium
XC at f=60 Hz, C=0.00005 F is approximately
1. A531 ohm
2. B53.1 ohm
3. C5.31 ohm
4. D0.531 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 53.1 ohm.
Q9Past Paper · PPSC/FPSC/CSSmedium
XC at f=50 Hz, C=0.0001 F is approximately
1. A318 ohm
2. B3.18 ohm
3. C0.318 ohm
4. D31.8 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 31.8 ohm.
Q10Past Paper · PPSC/FPSC/CSSmedium
XL at f=400 Hz, L=0.01 H is approximately
1. A251.3 ohm
2. B2.51 ohm
3. C0.251 ohm
4. D25.1 ohm
💡 Explanation:
XL = 2 pi f L = 25.1 ohm.
Q11Past Paper · PPSC/FPSC/CSSmedium
XL at f=50 Hz, L=0.2 H is approximately
1. A628.3 ohm
2. B6.28 ohm
3. C0.628 ohm
4. D62.8 ohm
💡 Explanation:
XL = 2 pi f L = 62.8 ohm.
Q12Past Paper · PPSC/FPSC/CSSeasy
Phasor representation of AC voltage uses
1. Arotating vector with magnitude and phase angle
2. Bscalar DC value only
3. Cbinary digits only
4. Dmagnetic flux density only
💡 Explanation:
Sinusoids map to complex phasors.
Q13Past Paper · PPSC/FPSC/CSSeasy
RMS value of sinusoidal voltage Vmax is
1. AVmax/sqrt(2)
2. BVmax times 2
3. CVmax squared
4. DVmax/2
💡 Explanation:
Vrms = Vm/sqrt(2).
Q14Past Paper · PPSC/FPSC/CSSmedium
Average power in AC consumed by resistor depends on
1. Apeak values only without cos phi
2. Bfrequency only
3. Creactive power only
4. DRMS voltage and RMS current and cos phi
💡 Explanation:
P = Vrms Irms cos phi.
Q15Past Paper · PPSC/FPSC/CSSeasy
A lagging power factor indicates
1. Ainductive load (current lags voltage)
2. Bcapacitive load
3. Cpurely resistive load
4. Dzero current
💡 Explanation:
Inductors cause lagging PF.
Q16Past Paper · PPSC/FPSC/CSSeasy
A leading power factor indicates
1. Acapacitive load (current leads voltage)
2. Binductive load
3. Cpurely resistive load
4. Dinfinite reactance
💡 Explanation:
Capacitors cause leading PF.
Q17Past Paper · PPSC/FPSC/CSSmedium
XL at f=50 Hz, L=0.1 H is approximately
1. A314.2 ohm
2. B3.14 ohm
3. C0.314 ohm
4. D31.4 ohm
💡 Explanation:
XL = 2 pi f L = 31.4 ohm.
Q18Past Paper · PPSC/FPSC/CSSmedium
XL at f=60 Hz, L=0.05 H is approximately
1. A188.5 ohm
2. B1.885 ohm
3. C18.85 ohm
4. D0.188 ohm
💡 Explanation:
XL = 2 pi f L = 18.85 ohm.
Q19medium
R=3 ohm, X=4 ohm in series: |Z| is
1. A7 ohm
2. B5 ohm
3. C1 ohm
4. D12 ohm
💡 Explanation:
|Z| = sqrt(3²+4²) = 5 ohm.
Q20Past Paper · PPSC/FPSC/CSSmedium
XL at f=100 Hz, L=0.02 H is approximately
1. A125.7 ohm
2. B12.56 ohm
3. C1.256 ohm
4. D0.125 ohm
💡 Explanation:
XL = 2 pi f L = 12.56 ohm.
Q21Past Paper · PPSC/FPSC/CSSmedium
XL at f=50 Hz, L=0.2 H is approximately
1. A628.3 ohm
2. B6.28 ohm
3. C0.628 ohm
4. D62.8 ohm
💡 Explanation:
XL = 2 pi f L = 62.8 ohm.
Q22Past Paper · PPSC/FPSC/CSSmedium
XL at f=400 Hz, L=0.01 H is approximately
1. A251.3 ohm
2. B2.51 ohm
3. C0.251 ohm
4. D25.1 ohm
💡 Explanation:
XL = 2 pi f L = 25.1 ohm.
Q23Past Paper · PPSC/FPSC/CSSmedium
XC at f=50 Hz, C=0.0001 F is approximately
1. A318 ohm
2. B3.18 ohm
3. C0.318 ohm
4. D31.8 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 31.8 ohm.
Q24Past Paper · PPSC/FPSC/CSSmedium
XC at f=60 Hz, C=0.00005 F is approximately
1. A531 ohm
2. B53.1 ohm
3. C5.31 ohm
4. D0.531 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 53.1 ohm.
Q25Past Paper · PPSC/FPSC/CSSmedium
XC at f=100 Hz, C=0.00001 F is approximately
1. A1590 ohm
2. B15.9 ohm
3. C1.59 ohm
4. D159 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 159 ohm.
Q26Past Paper · PPSC/FPSC/CSSmedium
XC at f=50 Hz, C=0.0002 F is approximately
1. A15.9 ohm
2. B159 ohm
3. C1.59 ohm
4. D0.159 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 15.9 ohm.
Q27medium
XC at f=60 Hz, C=0.00008 F is approximately
1. A33.2 ohm
2. B332 ohm
3. C3.32 ohm
4. D0.332 ohm
💡 Explanation:
XC = 1/(2 pi f C) = 33.2 ohm.
Q28Past Paper · PPSC/FPSC/CSSmedium
An R-C series circuit has impedance
1. AR plus XC always
2. BR minus XC
3. CXC only
4. Dsqrt(R squared + XC squared)
💡 Explanation:
Z = sqrt(R² + XC²).
Q29Past Paper · PPSC/FPSC/CSSmedium
An R-L series circuit has impedance
1. Asqrt(R squared + XL squared)
2. BR plus XL always
3. CR minus XL
4. DXL only
💡 Explanation:
Z = sqrt(R² + XL²).
Q30Past Paper · PPSC/FPSC/CSSmedium
In parallel resonance, impedance is
1. Aminimum
2. Bzero
3. Cequal to R always
4. Dmaximum
💡 Explanation:
Parallel LC tank has high Z at fr.
Q31medium
R=6 ohm, X=8 ohm in series: |Z| is
1. A14 ohm
2. B2 ohm
3. C48 ohm
4. D10 ohm
💡 Explanation:
|Z| = sqrt(6²+8²) = 10 ohm.
Q32medium
If P=100 W and phi=45 deg with same V I, power factor is
1. A0.29
2. B0.707
3. C1.41
4. D0.71
💡 Explanation:
PF = cos 45 = 0.707.
Q33Past Paper · PPSC/FPSC/CSSmedium
Phase angle for R-C series circuit is
1. Atan inverse (XC/R) leading
2. Btan inverse (R/XC) lagging
3. Czero always
4. D180 degrees
💡 Explanation:
Current leads voltage in RC.
Q34Past Paper · PPSC/FPSC/CSSmedium
Phase angle phi for R-L series circuit is
1. Atan inverse (R/XL)
2. Bzero always
3. Ctan inverse (XL/R)
4. D90 degrees always
💡 Explanation:
phi = arctan(XL/R) lagging.
Q35medium
R=5 ohm, X=12 ohm in series: |Z| is
1. A17 ohm
2. B7 ohm
3. C13 ohm
4. D60 ohm
💡 Explanation:
|Z| = sqrt(5²+12²) = 13 ohm.
Q36Past Paper · PPSC/FPSC/CSSeasy
In a purely resistive AC circuit, power factor is
1. Azero
2. Bleading
3. Clagging always
4. Dunity (1)
💡 Explanation:
phi = 0; cos phi = 1.
Q37medium
R=9 ohm, X=40 ohm in series: |Z| is
1. A49 ohm
2. B31 ohm
3. C41 ohm
4. D360 ohm
💡 Explanation:
|Z| = sqrt(9²+40²) = 41 ohm.
Q38medium
R=7 ohm, X=24 ohm in series: |Z| is
1. A25 ohm
2. B31 ohm
3. C17 ohm
4. D168 ohm
💡 Explanation:
|Z| = sqrt(7²+24²) = 25 ohm.

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AC Circuits and Power Factor MCQs 2026

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