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Physics Alternating Current Online Mcqs Test

Mustansar KhanLast Updated: October 13, 2025

Important Physics Alternating Current Question and Answer

Total Questions:	49
Time Allowed:	25 Minutes
Total Marks:	49
How to Attempt Test:	Please choose the right Option in MCQ-type question.
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Physics Alternating Current Practice Test Online With Explanation

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1. What is the purpose of phase analysis in AC circuits?

To measure current

To understand power distribution

To calculate resistance

To measure voltage

2. How does increasing the frequency affect capacitive reactance?

No effect

Becomes zero

Increases it

Decreases it

3. What is the frequency of AC used in the United States?

50 Hz

25 Hz

100 Hz

60 Hz

4. Which component in an AC circuit causes energy to be dissipated as heat?

Inductor

Capacitor

Resistor

Transformer

5. Which of the following waves has the highest energy?

Infrared

Visible light

Radio waves

Gamma rays

6. In an inductor-only AC circuit, the voltage:

Leads current by 180°

Lags current by 90°

Leads current by 90°

Is in phase with current

7. In an AC circuit with only a resistor, what is the phase difference between current and voltage?

180°

90°

45°

0°

8. Which electromagnetic wave has more penetrating power?

Ultraviolet

Infrared

Gamma rays

X-rays

9. Which EM wave is used in cancer treatment?

Gamma rays

Infrared

Microwaves

Ultraviolet

10. Which EM wave is used in radar systems?

Radio waves

X-rays

Microwaves

Infrared

11. What is the phase relationship between current and voltage in an inductive AC circuit?

Voltage lags current

Voltage and current are in phase

Voltage leads current

Current leads voltage

12. What happens to the power factor in a purely inductive or capacitive circuit?

It remains unchanged

It becomes 1

It becomes negative

It becomes zero

13. When AC passes through a capacitor, it:

Reverses direction

Is blocked completely

Passes with phase lag

Passes with phase lead

14. In which part of the electromagnetic spectrum does visible light lie?

Between infrared and ultraviolet

Between X-rays and gamma rays

Between ultraviolet and X-rays

Between microwaves and radio waves

15. What is the significance of phase angle in an AC circuit?

Shows the time difference between voltage and current

Determines direction

Determines speed

Shows the strength of the current

16. What is the result of the vector addition of current and voltage in an RLC circuit?

Phase angle

Impedance

Power factor

Reactance

17. Which EM wave is used in mobile communication?

Gamma rays

Infrared

Microwaves

X-rays

18. What happens when a capacitor is connected to an AC source?

It blocks current

It allows current with a phase lead

It acts like a resistor

It charges fully

19. What is the result of applying AC through a pure resistor?

Voltage and current are in phase

Current is zero

Current leads voltage

Voltage leads current

20. Which of the following AC circuit components stores energy in an electric field?

Capacitor

Transformer

Resistor

Inductor

21. Which electromagnetic wave is used in satellite communication?

Gamma rays

Infrared rays

Microwaves

X-rays

22. The EM wave with the shortest wavelength is:

Microwaves

Gamma rays

Ultraviolet

X-rays

23. Which of the following devices can cause a phase lead in an AC circuit?

Resistor

Inductor

Capacitor

Transformer

24. What causes phase difference in AC circuits?

Resistance only

Voltage drop

Only capacitance

Inductance and capacitance

25. What happens to current in an inductive AC circuit?

Is zero

Lags voltage

Is in phase

Leads voltage

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26. Which of the following AC circuit components stores energy in a magnetic field?

Diode

Resistor

Capacitor

Inductor

27. Which of the following is true in a capacitive AC circuit?

Current leads voltage

Voltage and current are in phase

Voltage leads current

Voltage lags current by 180°

28. In which case is the power factor of an AC circuit maximum?

Pure capacitor

Pure inductor

Pure resistor

RC circuit

29. What is the phase difference in an AC circuit with only a capacitor?

Voltage leads current by 90°

Voltage lags current by 90°

No phase difference

Voltage leads current by 180°

30. Which electromagnetic wave is responsible for sunburn?

Ultraviolet rays

Microwaves

Gamma rays

X-rays

31. Which wave has more energy than UV but less than gamma rays?

X-rays

Infrared

Microwaves

Radio waves

32. Which wave in the EM spectrum is used for medical imaging?

Infrared

Gamma rays

X-rays

Radio waves

33. Which of these quantities is the same for all types of EM waves in a vacuum?

Wavelength

Energy

Speed

Frequency

34. How does a capacitor behave in a DC circuit after a long time?

Acts as a conductor

Acts as an insulator

Increases current

Discharges quickly

35. Which electromagnetic wave is used in sterilizing surgical instruments?

Ultraviolet rays

Infrared rays

Microwaves

Radio waves

36. Which EM wave is used in remote controls?

Radio waves

X-rays

Infrared rays

Gamma rays

37. Which device is used to measure the frequency of AC?

Voltmeter

Ammeter

Frequency meter

Wattmeter

38. Which EM wave has a frequency just above visible light?

Ultraviolet

X-rays

Radio waves

Infrared

39. Which property is different among the different waves in the EM spectrum?

Medium

Direction

Frequency

Speed

40. In which component of an AC circuit does the current lead the voltage by 90°?

Resistor

Inductor

Transformer

Capacitor

41. Which EM wave is used in night vision equipment?

Microwaves

Ultraviolet

Infrared

Gamma rays

42. What is the waveform of typical alternating current?

Triangular wave

Constant wave

Square wave

Sine wave

43. What is meant by 'phase lag' in AC circuits?

Voltage is ahead of current

Voltage and current are in phase

Current is ahead of voltage

Both occur simultaneously

44. What determines the impedance of an RLC circuit?

Resistance, inductance, and capacitance

Resistance and capacitance

Only inductance

Only resistance

45. What is the unit of reactance in an AC circuit?

Ohm

Ampere

Henry

Volt

46. Which part of the EM spectrum is used for cooking in microwave ovens?

Radio waves

Ultraviolet

Microwaves

Infrared

47. The term “rms value” in AC stands for:

Resistance maximum supply

Radio mean speed

Root mean square

Radiant mechanical signal

48. Which of the following is not part of the electromagnetic spectrum?

X-rays

Microwaves

Sound waves

Infrared

49. Which property of AC allows it to be transmitted over long distances efficiently?

Can be stepped up or down using transformers

Ability to reverse direction

Constant voltage

Can be converted to DC

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Mustansar KhanLast Updated: October 13, 2025

Physics Alternating Current Online Mcqs Test

Important Physics Alternating Current Question and Answer

Physics Alternating Current Practice Test Online With Explanation

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