How long does one complete cycle of a 60 Hz waveform take?
Answer in ms.
Show the answer
16.67 ms
Period T = 1 ÷ f = 1 ÷ 60 = 0.01667 s. 0.01667 s × 1,000 = 16.67 ms.
Reference: AC fundamentals: period T = 1 ÷ f
TradeExamPro › Electrician › Electrical theory and calculations
AC theory practice questions
30 questions from the electrical theory and calculations practice test.
AC theory practice test
10 questions, graded as you go, with the reason for every answer. No sign-up.
What this covers
- Frequency
- RMS and peak values
- Reactance
- Phase relationships
- Impedance
- Power factor
- True, apparent and reactive power
- Power factor correction
Sample questions
What is the peak voltage of a 120 V RMS sine wave? (Use 1.414.)
Answer in V.
Show the answer
169.7 V
E peak = E rms × 1.414 = 120 × 1.414 = 169.7 V.
Reference: AC fundamentals: E peak = 1.414 × E rms
A sine wave has a peak value of 340 V. What is its RMS (effective) value?
- 481 V
- 217 V
- 240 V
- 170 V
Show the answer
C. 240 V
E rms = E peak × 0.707 = 340 × 0.707 = 240.4 V, about 240 V. 217 V uses 0.637, which gives the average value rather than the RMS value, and 481 V multiplies by 1.414 when it should divide.
Reference: AC fundamentals: E rms = 0.707 × E peak