Key relationship
v=V₀ sin(2πft); Vrms=V₀/√2; Irms=I₀/√2.
Physics · Class 12
AC peak and RMS
RMS is the DC-equivalent heating value for a resistor. It is not the mean voltage of a symmetric sinusoid, whose mean over a whole cycle is zero.
Open the interactive experiment →AC peak and RMS
சைன் AC-இன் RMS மதிப்பு உச்ச மதிப்பு/√2. முழுச் சுழற்சி சராசரி மின்னழுத்தம் பூஜ்யம்.
Key notes, relationships and model limits
Remember
RMS is the DC-equivalent heating value for a resistor. It is not the mean voltage of a symmetric sinusoid, whose mean over a whole cycle is zero.
Common trap
V₀/√2 is the RMS value of a sinusoid, not of every waveform. RMS and mean voltage are different averages.
Model limits
Steady sinusoidal series LCR circuit; peak control is not RMS. RMS formula holds for a sinusoid only.
What you will learn
Use the controls and plotted relation to explain ac peak and rms.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
Vpeak=100 V gives Vrms=100/√2≈70.71 V.
Why this matters
The model connects ac peak and rms with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
A sinusoidal AC with peak 100 V has RMS?
- 100 V.
- Approximately 70.7 V.
- 50 V.
Read the explanation
Approximately 70.7 V.
Course connection: Class XII Chapter 7. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.