The root mean square value of an alternating current is
Correct answer: B. the peak value divided by the square root of 2
- A. equal to its peak value
- B. the peak value divided by the square root of 2
- C. the peak value multiplied by 2
- D. always zero
Explanation
The rms value is about 0.707 of the peak and is defined as the steady direct current that would dissipate the same power in a given resistor. Mains electricity quoted as 220 V is an rms figure, so the peak is around 311 V, which is why insulation must be rated well above the nominal value. The simple average over a full cycle is zero, which is why the rms measure is needed at all.
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About Phase of Alternating Current
Phase describes the position of an alternating voltage or current within its cycle and the phase difference between two sinusoidal quantities. The topic covers in phase signals, phase angle and lead or lag in resistive, inductive and capacitive circuits, rather than the amplitude or frequency of the supply.
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