Free Alternating Current MCQs with Answers
22 Alternating Current MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
22 questions · page 3 of 3
21. A phase difference of 90 degrees is equal to:
- A. pi radians
- B. pi/2 radians
- C. 2 pi radians
- D. pi/4 radians
Explanation: A complete cycle is 360 degrees or 2 pi radians, so 90 degrees is a quarter of a cycle, that is pi over 2 radians. This is the phase difference between current and voltage in a purely capacitive or purely inductive AC circuit, which is why no net power is dissipated in either. The Greek letter did not print cleanly in the original paper.
Correct answer: pi/2 radians22. The wave that has the highest frequency and penetrating power is
- A. X-rays
- B. Ultraviolet rays
- C. Gamma rays
- D. Microwaves
Explanation: Gamma rays sit at the extreme short wavelength end of the electromagnetic spectrum, so they carry the highest frequency and photon energy and need several centimetres of lead to attenuate them. X rays are next and overlap gamma rays in energy, the difference being origin: gamma from the nucleus, X rays from electron transitions or deceleration. Microwaves are at the low energy end.
Correct answer: Gamma rays