Step-by-step walkthrough
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
Step 1
Read the peak value off your source, datasheet, or oscilloscope — make sure it's peak, not peak-to-peak.
Step 2
Pick the waveform shape that matches your signal; mains power and most AC sources are sine waves.
Step 3
Use the RMS value for power calculations and the average value when you're specifically working with a rectified/filtered signal.
120V is the RMS value — the number that matters for power delivery and what's printed on outlets and appliances. The actual voltage swings between +170V and -170V on a sine wave, which is exactly the example above.
A square wave spends 100% of its time at either +peak or -peak with no time in between, so its average power is identical to a DC source at that peak value — there's no time-averaging effect the way there is with a sine or triangle wave.
