RC circuit simulator
Watch a capacitor charge, one time constant at a time.
The RC charging curve is the first exponential every electronics student meets. Build the loop, run a transient analysis, and the scope traces it live — with the maths matching the plot.
The time constant, at a glance
With R in kΩ and C in µF, the time constant τ = R × C comes out directly in milliseconds — so 10 kΩ and 10 µF give exactly 100 ms.
63.2%
charged after 1τ
86.5%
charged after 2τ
95.0%
charged after 3τ
99.3%
charged after 5τ
Questions
- What is the RC time constant?
- It is τ = R × C, the time a capacitor takes to reach about 63% of its final voltage when charging through a resistor. After five time constants it is roughly 99% charged — effectively settled.
- Can I see the charging curve?
- Yes. Run a transient analysis and the voltage probe traces Vc(t) = Vs·(1 − e^(−t/τ)) on the oscilloscope in real time. It is a solved curve, not a drawn one.
- How do I pick R and C for a target time?
- Any R and C whose product gives your target τ will do; the choice trades current draw against capacitor size. The RC time constant calculator turns R and C into τ and the 63% and 99% times instantly.
- Does it handle discharging too?
- Yes. The same exponential governs discharge — the capacitor falls to 37% of its start after one time constant. Build the discharge path and run the transient to watch it decay.