Discharging a capacitor through a resistor provides a voltage curve that drops extremely fast at first and then changes very slowly towards the end of the discharge.

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Diagram

Video below shows how I build this circuit on a breadboard.

Time constant is usually indicated by it’s initials (TC) or the greek letter tau ( τ ).

RC time constant is determined by the capacitance of the capacitor in farads times the resistance in ohms. τ = RC

First time constant changes from the starting voltage to about 63% of the final voltage. Each time constant after that changes about 63% of the remaining voltage. After 5 time constants, the voltage is practically completely changed and therefore the capacitor is usually declared as being fully charged or discharged after 5 time constants.





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Video

Quick discharging capacitor RC time constant circuit schematic to breadboard build and oscilloscope



Updated video and diagram:

A 1,000µF (same as 0.001F) capacitor with a 1,000Ω resistor has a time constant of 1 second. Therefore it will take about 5 seconds to go from 5 volts to 0V.

Discharging capacitor component RC time constant curve oscilloscope measured



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