AC Circuit Builder

Displays voltage (red) and current (blue) as time-varying sinusoidal waveforms across the selected component(s). This lets you see the CIVIL convention in action — in a Capacitor I leads V, and V leads I in an inductor (L).

1. Tick the V-I Waveform checkbox to show the graph.
2. Click any component to select it — the graph shows its V and I waveforms.
3. Click the next adjacent component to extend the selection and see combined voltage.
4. Click a component at either end to remove it from the selection.
Components must form a continuous chain in the same branch.

Drag the title bar to reposition the small graph.
Click the graph body to enlarge it full-size.
Click outside the enlarged graph to shrink it back.
When enlarged, additional analysis buttons appear in the top-right corner.

Appears when the graph is enlarged. The button shows a small phasor icon (two arrows with an arc) in the top-right corner. Click it to open a phasor diagram showing the phase relationship between V and I as rotating vectors.
Play/Pause — animates the phasors rotating at angular frequency ω, with sine wave traces drawn alongside.
Works for single or multiple selected components — V shows the combined voltage across the selection and I shows the current through them.

Appears when a single capacitor is selected and the graph is enlarged. Click the Q button to open the charge graph.
Shows Q(t) = C × V(t) — how charge on the capacitor varies with time. A gradient marker follows the curve showing the instantaneous slope dQ/dt, which equals the current I.
Where the Q curve is steepest, current is maximum. Where Q is at a peak or trough, current is zero. This visually demonstrates why I leads V by 90° in a capacitor.

Appears when a single inductor is selected and the graph is enlarged. Click the L button to open the inductor graph.
Shows V = L × dI/dt — a gradient marker follows the current curve showing how its slope determines the voltage. Where current changes fastest (steepest gradient), voltage is at its peak. Where current is at a peak or trough, voltage is zero. This visually demonstrates why V leads I by 90° in an inductor.

Appears when a single component (resistor, capacitor, or inductor) is selected and the graph is enlarged. Click the P button to open the power graph.

Interactive slider — drag to progressively reveal the power curve P(t) = V × I. As you sweep across time you see:
• A red dot on V, a blue dot on I, and a gold dot on P, each showing their instantaneous value.
• Green shading where P > 0 (energy being stored or dissipated).
• Red shading where P < 0 (energy being returned to the supply).

For capacitors and inductors: green and red areas cancel every half-cycle, giving Mean Power = 0. An energy bar on the right shows the energy stored (½CV² or ½LI²) rising and falling — ending exactly where it started after one full cycle.

For resistors: power is always positive (all green shading). There is no energy bar because energy is dissipated as heat, not stored. The mean power line shows the actual power consumed.