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Physics
AC electricity and phase relationships
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Build AC circuits and connect rotating phasors with each component’s voltage and current waveforms.
Circuit type
Motion is slowed by a factor of 100. Frequency uses physical time.
Current leads voltage
φ = voltage phase − current phase
For a capacitor, i = C·du/dt: i leads u by π/2 (a quarter cycle). When u = 0 the capacitor charges or discharges fastest, so i peaks.
t = 0 ms
- u
- 0 V
- i
- 3.142 A
| Quantity | Peak | RMS |
|---|---|---|
| Voltage | 100 V | 70.71 V |
| Current | 3.142 A | 2.221 A |
U = U₀/√2 · I = I₀/√2
- Impedance Z
- 31.83 Ω
- Period T
- 20 ms
- Mean power P
- 0 W
Model notes
- The sinusoidal source and R, L, C components are ideal. Only steady-state AC is represented, without switching transients.
- φ = voltage phase − current phase; positive φ means current lags. In assembled circuits uAB = VA − VB, load current runs A→B; source readings use delivered current (B→A through the source).
- Phasors and graphs are normalized separately by U₀ and I₀ to compare phase; the i phasor and curve are always drawn at 0.62 of the u height only to tell them apart. Voltage and current have different units, so lengths are not compared; real values are on the graph axes and the ammeter (RMS).
- Motion is slowed by a factor of 100. In the circuit drawing, yellow dots (conventional current) swing back and forth with i(t), faster for a larger I₀ but limited for readability; this is not the electron drift speed. The +/− marks at the source and on the capacitor plates only show the sign of the instantaneous voltage. Control ranges are limits of this resource, not physical limits of AC circuits.
- The workbench supports one sinusoidal source at a common frequency. Phase is undefined at zero voltage or current; singular ideal circuits report no unique steady state. Zero source current need not mean zero branch current. Real losses and switching transients are omitted; arrows illustrate instantaneous current direction, not electrons crossing a capacitor.