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. Which electromagnetic wave is used in sterilizing surgical instruments?

Infrared rays

Ultraviolet rays

Microwaves

Radio waves

2. Which electromagnetic wave is used in satellite communication?

Gamma rays

Infrared rays

X-rays

Microwaves

3. The EM wave with the shortest wavelength is:

Gamma rays

X-rays

Microwaves

Ultraviolet

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

Discharges quickly

Acts as a conductor

Increases current

Acts as an insulator

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

X-rays

Infrared

Ultraviolet

Radio waves

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

Current leads voltage

Voltage leads current

Current is zero

Voltage and current are in phase

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

Henry

Ohm

Ampere

Volt

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

Voltage and current are in phase

Current is ahead of voltage

Voltage is ahead of current

Both occur simultaneously

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

Microwaves

X-rays

Radio waves

Infrared

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

It allows current with a phase lead

It blocks current

It charges fully

It acts like a resistor

11. Which electromagnetic wave has more penetrating power?

Infrared

Gamma rays

Ultraviolet

X-rays

12. Which electromagnetic wave is responsible for sunburn?

Microwaves

Ultraviolet rays

X-rays

Gamma rays

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

Can be stepped up or down using transformers

Constant voltage

Can be converted to DC

Ability to reverse direction

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

0°

180°

45°

90°

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

Inductor

Resistor

Transformer

Capacitor

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

Determines direction

Determines speed

Shows the time difference between voltage and current

Shows the strength of the current

17. Which EM wave is used in remote controls?

Gamma rays

X-rays

Infrared rays

Radio waves

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

Wavelength

Frequency

Energy

Speed

19. Which EM wave is used in radar systems?

Microwaves

Infrared

X-rays

Radio waves

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

Transformer

Inductor

Resistor

Capacitor

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

Power factor

Phase angle

Impedance

Reactance

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

Infrared

Radio waves

Visible light

Gamma rays

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

Voltage and current are in phase

Voltage lags current by 180°

Voltage leads current

Current leads voltage

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

Lags current by 90°

Leads current by 90°

Is in phase with current

Leads current by 180°

25. What is the waveform of typical alternating current?

Triangular wave

Constant wave

Square wave

Sine wave

Page 2 of 2

26. How does increasing the frequency affect capacitive reactance?

Increases it

Decreases it

Becomes zero

No effect

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

Microwaves

Sound waves

X-rays

Infrared

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

Between X-rays and gamma rays

Between infrared and ultraviolet

Between ultraviolet and X-rays

Between microwaves and radio waves

29. What causes phase difference in AC circuits?

Resistance only

Voltage drop

Inductance and capacitance

Only capacitance

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

Microwaves

Ultraviolet

Gamma rays

Infrared

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

Radiant mechanical signal

Resistance maximum supply

Radio mean speed

Root mean square

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

It becomes 1

It becomes zero

It becomes negative

It remains unchanged

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

Direction

Medium

Speed

Frequency

34. 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

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

Resistor

Transformer

Inductor

Capacitor

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

No phase difference

Voltage leads current by 90°

Voltage lags current by 90°

Voltage leads current by 180°

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

Is in phase

Leads voltage

Is zero

Lags voltage

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

Transformer

Capacitor

Resistor

Inductor

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

Pure capacitor

Pure inductor

Pure resistor

RC circuit

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

Diode

Resistor

Capacitor

Inductor

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

Gamma rays

X-rays

Radio waves

Infrared

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

To measure voltage

To measure current

To understand power distribution

To calculate resistance

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

Ultraviolet

Infrared

Microwaves

Radio waves

44. Which EM wave is used in cancer treatment?

Ultraviolet

Infrared

Microwaves

Gamma rays

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

Wattmeter

Ammeter

Frequency meter

Voltmeter

46. Which EM wave is used in mobile communication?

Gamma rays

Microwaves

Infrared

X-rays

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

60 Hz

100 Hz

25 Hz

50 Hz

48. When AC passes through a capacitor, it:

Passes with phase lead

Reverses direction

Is blocked completely

Passes with phase lag

49. What determines the impedance of an RLC circuit?

Only resistance

Resistance and capacitance

Resistance, inductance, and capacitance

Only inductance

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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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