19.3.2—Τ = RC for the time constant for a capacitor discharging through a resistor

For a resistor R and capacitor C, τ=RC. After one time constant in a discharge, the relevant quantity has fallen to e⁻¹≈37% of its initial value.

Larger R or C makes the response slower. Identify the effective resistance seen by the capacitor, not every resistor in the diagram.

R=2.0 kΩ and C=100 μF gives τ=0.20 s.

τ is not the time to reach exactly zero; exponential decay approaches zero asymptotically.