AC alternates as a sine wave while DC holds steady, and the RMS voltage is what makes them comparable. Drag the sliders below to change the peak voltage, frequency and load resistance, and watch the sine wave, the flat DC line and the power readouts respond in real time.
This simulator puts alternating and direct current on the same oscilloscope so you can compare them directly. The Peak voltage slider sets how high the gold AC sine reaches; the Frequency slider sets how fast it alternates; and the Load resistance slider sets how much current flows. The mode buttons let you view AC alone, DC alone, or both together, and the flat mist line always sits at the AC wave's RMS value — the level at which a steady DC supply would do exactly the same job.
Two things are worth watching closely. First, the RMS voltage readout: the simulator is solving Vrms = V0/sqrt(2), so it tracks the peak, not the frequency. Second, the average power readout, computed as P = Vrms²/R — this is where the surprise lives. Slide the frequency up and down and the wave visibly speeds up, the period shrinks and the reversals-per-second climb, yet the RMS voltage and the average power do not move at all. The two identical elements glow at the same steady brightness because power is set by the RMS value and the resistance, never by how fast the wave wiggles.
That is the misconception this page exists to kill: the belief that a faster alternating current delivers more power. It does not. Frequency changes the timing of the wave, not its strength. Raise the peak voltage instead and the power jumps as the square of the voltage; raise the resistance and both current and power fall. Put exact numbers to any setting with the RMS voltage calculator, read the full comparison in AC vs DC Current: What's the Difference?, connect it to current and resistance through Ohm's law, or open another model from the full simulation collection.
Because average power depends on the RMS voltage and the resistance, not on how fast the wave alternates. Moving the frequency slider changes the period and the number of reversals per second, but the peak voltage — and therefore the RMS value, Vrms = V0/sqrt(2) — stays the same, so P = Vrms squared over R does not move. It surprises most people, which is exactly why the simulator makes you watch the power readout hold still while the wave visibly speeds up.
The flat mist-coloured line is the DC voltage, and the simulator pins it to the AC wave's RMS value. That is the whole point: a DC supply at the RMS voltage delivers the same average power as the alternating one, which is why the two glowing elements shine equally brightly. The RMS value is the honest DC-equivalent of an AC voltage.
Because the RMS is an average-power measure, not the maximum. A sine wave only touches its peak for an instant each cycle and spends most of the time nearer zero, so its effective (RMS) value is lower — exactly the peak divided by sqrt(2), about 0.707 of it. Mains quoted as 230 V RMS actually peaks near 325 V; the simulator shows both at once.
In AC the current changes direction every half cycle, so it reverses twice per cycle — a 50 Hz supply reverses 100 times a second. The readout shows this as two times the frequency. In the DC wire the electrons drift steadily one way; in the AC wire they jitter back and forth in place, which is what those reversals look like at the level of the charges.
No — the slider stops at 1 Hz. Zero frequency would mean the period 1/f is infinite, which is really just DC (a wave that never alternates), and it would also make the period readout undefined. To explore true DC, switch the view to the DC mode instead, where the voltage is held steady at the RMS value.