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.
Test Helpful For:	Physics Test ECAT Test MDCAT Test FPSC/PPSC/SPSC/KPPSC/BPSC/AJKPSC/NTS Physics Interview Question Answer

Physics Alternating Current Practice Test Online With Explanation

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

Resistance maximum supply

Root mean square

Radiant mechanical signal

Radio mean speed

2. What determines the impedance of an RLC circuit?

Resistance, inductance, and capacitance

Only resistance

Resistance and capacitance

Only inductance

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

Visible light

Gamma rays

Radio waves

Infrared

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

Ohm

Ampere

Volt

Henry

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

Voltage and current are in phase

Voltage leads current

Current leads voltage

Voltage lags current by 180°

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

To measure voltage

To calculate resistance

To measure current

To understand power distribution

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

100 Hz

50 Hz

60 Hz

25 Hz

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

Inductor

Diode

Resistor

Capacitor

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

Capacitor

Resistor

Transformer

Inductor

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

It becomes zero

It remains unchanged

It becomes 1

It becomes negative

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

Infrared

X-rays

Microwaves

Sound waves

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

Infrared

Ultraviolet

X-rays

Radio waves

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

Infrared

X-rays

Microwaves

Radio waves

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

Ability to reverse direction

Constant voltage

Can be converted to DC

Can be stepped up or down using transformers

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

No phase difference

Voltage leads current by 90°

Voltage leads current by 180°

Voltage lags current by 90°

16. 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

17. Which EM wave is used in mobile communication?

X-rays

Infrared

Microwaves

Gamma rays

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

Transformer

Inductor

Resistor

Capacitor

19. When AC passes through a capacitor, it:

Reverses direction

Is blocked completely

Passes with phase lag

Passes with phase lead

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

It charges fully

It acts like a resistor

It blocks current

It allows current with a phase lead

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

Impedance

Reactance

Power factor

Phase angle

22. How does increasing the frequency affect capacitive reactance?

Increases it

Becomes zero

Decreases it

No effect

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

Voltage and current are in phase

Voltage is ahead of current

Current is ahead of voltage

Both occur simultaneously

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

Is in phase

Leads voltage

Is zero

Lags voltage

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

Inductor

Transformer

Resistor

Capacitor

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

Capacitor

Resistor

Transformer

Inductor

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

Acts as an insulator

Acts as a conductor

Discharges quickly

Increases current

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

Voltage lags current

Voltage leads current

Voltage and current are in phase

Current leads voltage

29. Which electromagnetic wave has more penetrating power?

Gamma rays

Infrared

Ultraviolet

X-rays

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

Pure inductor

RC circuit

Pure capacitor

Pure resistor

31. The EM wave with the shortest wavelength is:

Ultraviolet

Gamma rays

X-rays

Microwaves

32. What is the waveform of typical alternating current?

Constant wave

Triangular wave

Sine wave

Square wave

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

Ultraviolet

Microwaves

Infrared

Gamma rays

34. Which EM wave is used in radar systems?

Radio waves

Infrared

Microwaves

X-rays

35. Which EM wave is used in cancer treatment?

Ultraviolet

Infrared

Gamma rays

Microwaves

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

Medium

Direction

Speed

Frequency

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

Is in phase with current

Leads current by 90°

Lags current by 90°

Leads current by 180°

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

180°

45°

0°

90°

39. Which EM wave is used in remote controls?

Infrared rays

X-rays

Radio waves

Gamma rays

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

Determines speed

Shows the time difference between voltage and current

Determines direction

Shows the strength of the current

41. Which electromagnetic wave is responsible for sunburn?

Ultraviolet rays

X-rays

Gamma rays

Microwaves

42. Which electromagnetic wave is used in satellite communication?

Microwaves

X-rays

Infrared rays

Gamma rays

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

Ultraviolet rays

Radio waves

Microwaves

Infrared rays

44. What causes phase difference in AC circuits?

Inductance and capacitance

Resistance only

Only capacitance

Voltage drop

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

Voltmeter

Frequency meter

Wattmeter

Ammeter

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

X-rays

Radio waves

Infrared

Gamma rays

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

Speed

Wavelength

Frequency

Energy

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

Infrared

Microwaves

Ultraviolet

Radio waves

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

Between ultraviolet and X-rays

Between microwaves and radio waves

Between infrared and ultraviolet

Between X-rays and gamma rays

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Mustansar KhanLast Updated: October 13, 2025

Important Physics Alternating Current Question and Answer

Physics Alternating Current Practice Test Online With Explanation

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