AC Circuits Lab
This lab lets you assemble resistors, capacitors and inductors into AC circuits and watch the voltage and current traces respond. Because the phase relationship between them is drawn directly on the graph, the abstract idea of current leading or lagging voltage becomes something you can see.
How to use this simulation
- Build series and parallel combinations of R, L and C
- Sweep the supply frequency
- Adjust each component value independently
What to look for
- Capacitive reactance falls as frequency rises, while inductive reactance climbs
- Current reaches its maximum at the resonant frequency, where the two reactances cancel
- The phase shift flips sign as you tune through resonance
The physics behind it
A resistor keeps current and voltage in phase. A capacitor makes current lead the voltage by 90° with reactance X_C = 1/(2πfC); an inductor makes it lag by 90° with X_L = 2πfL. Combining them gives impedance Z = √(R² + (X_L − X_C)²), and when X_L equals X_C the circuit is at resonance and Z falls to just R.