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

Speed

Frequency

Medium

Direction

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

To measure voltage

To understand power distribution

To measure current

To calculate resistance

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

Sound waves

X-rays

Microwaves

Infrared

4. What determines the impedance of an RLC circuit?

Only inductance

Resistance and capacitance

Resistance, inductance, and capacitance

Only resistance

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

Constant voltage

Can be stepped up or down using transformers

Can be converted to DC

Ability to reverse direction

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

60 Hz

25 Hz

50 Hz

100 Hz

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

Voltage and current are in phase

Voltage leads current

Voltage lags current

Current leads voltage

8. How does increasing the frequency affect capacitive reactance?

Becomes zero

No effect

Decreases it

Increases it

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

Pure resistor

Pure inductor

RC circuit

Pure capacitor

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

Gamma rays

Ultraviolet

Infrared

Microwaves

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

Resistance maximum supply

Radio mean speed

Root mean square

Radiant mechanical signal

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

Energy

Speed

Frequency

Wavelength

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

Shows the strength of the current

Shows the time difference between voltage and current

Determines speed

Determines direction

14. When AC passes through a capacitor, it:

Passes with phase lead

Reverses direction

Is blocked completely

Passes with phase lag

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

X-rays

Infrared

Gamma rays

Radio waves

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

Lags voltage

Leads voltage

Is zero

Is in phase

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

Microwaves

Ultraviolet rays

Infrared rays

Radio waves

18. The EM wave with the shortest wavelength is:

X-rays

Microwaves

Ultraviolet

Gamma rays

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

Radio waves

X-rays

Ultraviolet

Infrared

20. What is the waveform of typical alternating current?

Square wave

Sine wave

Constant wave

Triangular wave

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

Wattmeter

Voltmeter

Ammeter

Frequency meter

22. What causes phase difference in AC circuits?

Only capacitance

Voltage drop

Inductance and capacitance

Resistance only

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

Microwaves

Radio waves

Infrared

Ultraviolet

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

Resistor

Capacitor

Inductor

Transformer

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

Infrared

X-rays

Microwaves

Radio waves

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

Leads current by 90°

Leads current by 180°

Is in phase with current

Lags current by 90°

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

Voltage lags current by 90°

Voltage leads current by 90°

No phase difference

Voltage leads current by 180°

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

Inductor

Capacitor

Resistor

Diode

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

It becomes negative

It becomes 1

It remains unchanged

It becomes zero

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

Capacitor

Transformer

Inductor

Resistor

31. Which EM wave is used in mobile communication?

Microwaves

X-rays

Gamma rays

Infrared

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

Voltage and current are in phase

Voltage leads current

Voltage lags current by 180°

Current leads voltage

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

Voltage and current are in phase

Current leads voltage

Current is zero

Voltage leads current

34. Which electromagnetic wave is responsible for sunburn?

Gamma rays

X-rays

Microwaves

Ultraviolet rays

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

Ampere

Ohm

Volt

Henry

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

Acts as a conductor

Increases current

Acts as an insulator

Discharges quickly

37. Which EM wave is used in radar systems?

Microwaves

Infrared

Radio waves

X-rays

38. Which EM wave is used in cancer treatment?

Ultraviolet

Microwaves

Gamma rays

Infrared

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

Both occur simultaneously

Current is ahead of voltage

Voltage and current are in phase

Voltage is ahead of current

40. Which electromagnetic wave is used in satellite communication?

Infrared rays

Microwaves

Gamma rays

X-rays

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

Gamma rays

Infrared

Radio waves

Visible light

42. Which electromagnetic wave has more penetrating power?

Infrared

Ultraviolet

X-rays

Gamma rays

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

Capacitor

Resistor

Transformer

Inductor

44. Which EM wave is used in remote controls?

Radio waves

Infrared rays

X-rays

Gamma rays

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

Between X-rays and gamma rays

Between ultraviolet and X-rays

Between microwaves and radio waves

Between infrared and ultraviolet

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

It charges fully

It blocks current

It acts like a resistor

It allows current with a phase lead

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

45°

180°

90°

0°

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

Power factor

Phase angle

Reactance

Impedance

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

Inductor

Capacitor

Resistor

Transformer

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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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