The RC time constant, represented as **τ** (tau), is a measure used in electrical engineering to quantify the time it takes for a capacitor, through a resistor, to charge to approximately 63.2% of the voltage supply or discharge to about 36.8% of its initial charge voltage.

**Calculator**

Enter

- Resistance
**R**with units ohm (Ω) - Capacitance
**C**with units Farad (F)

**Formula**

**τ = R*C**

Where

**R**is the resistance in ohm (Ω)**C**is the capacitance in Farad (F)**τ**is the time constant in seconds

**Example Calculation**

For a resistor value of 1 ohm and Capacitor value of 10 µF, the time constant is 10 µs.

**Application**

The significance of the **RC time constant** lies in its utility for predicting how quickly a circuit responds to a change in voltage.

For instance, in a **charging capacitor** scenario, the voltage across the capacitor at any time ( t ) can be calculated using the formula:

**Vc = Vi (1-e ^{-t/τ})**

where,

**Vi**= Input Voltage**τ**= time constant**Vc**= voltage at the capacitor at time**t**

time constant **τ = RC**, where **R** is resistance and **C** is capacitance.

Similarly, for a discharging capacitor, the voltage across it decreases over time following the exponential decay formula:

**V = Vo*e ^{−t/RC}**

The time constant time constant **τ = RC**, where **R** is resistance and **C** is capacitance. The time **t **is typically specified as a multiple of the time constant.

**t = RC*Log _{e}(Vo/V)**

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