Engineering Board Exam Reviewer · Alternating Current and Voltage · hard
How long does it take a 400 Hz sine voltage, starting at zero, to reach 70.7% of its peak value for the first time?
- 0.625 ms
- 1.25 ms
- 1.77 ms
- 0.312 ms
Answer
D. 0.312 ms
Solution
70.7% of the peak occurs at =0.707, so =45°. T=1/400=2.5 ms, so t=45°/360°T=2.5/8=0.312 ms.
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