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AC Circuits Test

Class 12 Physics - Section B

Please enter your first name to begin the test. This test contains 15 multiple-choice questions and 10 numerical problems on Alternating Current concepts.

AC Circuits Test

Welcome, ! Good luck with your test.

Instructions: This test contains 15 multiple-choice questions and 10 numerical problems. Select the best answer for each question. After completing all questions, click "Submit Answers" to see your score and feedback.

Time: Approximately 45 minutes

Multiple Choice Questions (1-15)

1. The RMS value of alternating current is equal to:

Peak value

Peak value / √2

Peak value × √2

Average value

2. In a purely inductive AC circuit, the current:

Leads the voltage by 90°

Lags the voltage by 90°

Is in phase with voltage

Leads the voltage by 45°

3. The power factor in an AC circuit is defined as:

R/Z

Z/R

X_L/R

X_C/R

4. In a series LCR circuit at resonance:

Impedance is maximum

Current is minimum

Power factor is zero

Impedance is minimum

5. The unit of inductive reactance is:

Henry

Ohm

Farad

Siemens

6. In a purely capacitive AC circuit, the current:

Leads the voltage by 90°

Lags the voltage by 90°

Is in phase with voltage

Leads the voltage by 45°

7. The resonant frequency of a series LCR circuit is given by:

1/(2π√(LC))

2π√(LC)

1/(2πRC)

2π/√(LC)

8. The average power consumed in an AC circuit is given by:

V_rms × I_rms

V_rms × I_rms × cosφ

V₀ × I₀

V₀ × I₀ × sinφ

9. The capacitive reactance of a capacitor in an AC circuit:

Increases with frequency

Decreases with frequency

Is independent of frequency

Is zero at resonance

10. In an AC circuit with R, L, and C connected in series, the impedance is given by:

R + X_L + X_C

√(R² + (X_L + X_C)²)

√(R² + (X_L - X_C)²)

√(X_L² + X_C²)

11. The phase angle between current and voltage in a purely resistive AC circuit is:

0°

90°

45°

180°

12. The quality factor (Q-factor) of a series resonant circuit is given by:

R/√(L/C)

(1/R)√(L/C)

R√(LC)

1/(R√(LC))

13. The average value of AC over a complete cycle is:

I₀

I₀/√2

2I₀/π

Zero

14. In an AC circuit, the wattless component of current is due to:

Resistance

Inductance

Capacitance

Both inductance and capacitance

15. The form factor of AC is defined as:

RMS value / Average value

Peak value / RMS value

Peak value / Average value

Average value / RMS value

Numerical Problems (16-25)

16. An alternating voltage is given by V = 200 sin(314t) volts. Calculate its RMS value.

141.4 V

200 V

282.8 V

100 V

17. A capacitor of 100 μF is connected to an AC source of 220 V, 50 Hz. Find the capacitive reactance.

15.9 Ω

31.8 Ω

63.7 Ω

127.3 Ω

18. An inductor of 0.5 H is connected to an AC source of 220 V, 50 Hz. Calculate the inductive reactance.

31.4 Ω

62.8 Ω

157 Ω

314 Ω

19. A series LCR circuit has R = 10 Ω, L = 0.1 H, and C = 50 μF. Calculate the resonant frequency.

22.5 Hz

35.6 Hz

50.3 Hz

71.2 Hz

20. An AC circuit has a voltage V = 200 sin(100πt) and current I = 10 sin(100πt - π/3). Find the power factor.

0.5

0.707

0.866

1.0

21. In an AC circuit, the peak value of current is 10 A. What is its RMS value?

7.07 A

10 A

14.14 A

20 A

22. A 100 Ω resistor is connected to a 220 V, 50 Hz AC supply. What is the RMS value of current?

1.1 A

2.2 A

3.1 A

4.4 A

23. In a series LCR circuit, R = 30 Ω, X_L = 40 Ω, and X_C = 40 Ω. What is the impedance of the circuit?

30 Ω

50 Ω

70 Ω

110 Ω

24. An AC circuit has V_rms = 220 V, I_rms = 5 A, and power factor = 0.8. What is the power consumed?

440 W

660 W

880 W

1100 W

25. The average value of AC over half cycle for a sinusoidal current with peak value 14.14 A is:

9 A

10 A

11 A

12 A

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