Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
RMS current (Root Mean Square current) is the effective value of an alternating current (AC). It represents the equivalent direct current (DC) that would produce the same power dissipation in a resistive load.
5 Must Know Facts For Your Next Test
RMS stands for Root Mean Square, a statistical measure of the magnitude of a varying quantity.
The RMS value of an AC current is calculated as $I_{rms} = \frac{I_{peak}}{\sqrt{2}}$ for a sinusoidal wave.
RMS values are used because they provide a meaningful way to compare AC and DC currents in terms of their ability to do work or produce heat.
For non-sinusoidal waveforms, calculating RMS involves integrating the square of the instantaneous values over one period and then taking the square root.
The RMS current is crucial in determining power in AC circuits, as power ($P$) is given by $P = I_{rms}^2 R$ where $R$ is resistance.