Find the time constant τ = RC and the capacitor voltage while charging from 0 toward the supply V₀.
| τ (s) | – |
| Voltage (V) | – |
Use this calculator for a series RC circuit charging from an empty capacitor toward a DC supply. The voltage is V(t) = V₀ (1 − e^(−t/τ)), where τ = R C. After one time constant the voltage is about 63% of V₀; after 5τ it is essentially full.
A 5 V supply, 10 kΩ and 1 μF give τ = 10 ms. At t = 10 ms the voltage is about 3.16 V. Resistance is in ohms and capacitance in farads (1 μF is 0.000001 F). The supply’s internal resistance is ignored. This is charging from 0, not a discharge from V₀.
Supply (V): Final voltage the capacitor heads toward, in volts.
R (Ω): Series resistance in ohms, greater than zero.
C (F): Capacitance in farads, greater than zero. 1 μF is 1e-6 F.
Time (s): Time after connecting the supply, in seconds, zero or more.
τ (s): Time constant R C, in seconds.
Voltage (V): Capacitor voltage at that time, in volts.
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