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.
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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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.
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