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.
Brief circuit schematics with short video – List of pages
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Video below shows how I build this circuit on a breadboard.
Screwdriver set that I use in my videos.
- 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 almost completely changed and therefore the capacitor is usually declared as being fully charged or discharged after 5 time constants.
Updated video and diagram:
White version of the oscilloscope that I use in many of my recent videos.
A 1,000µF (same as 0.001F) capacitor and 1000Ω resistor have a time constant of 1 second. Therefore it will take about 5 seconds to go from 5 volts to approx. 0V.
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