Using a steady voltage to charge a capacitor through a resistance, and also discharging a capacitor through a resistance, creates what is called the RC time constant.
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Nice looking larger value capacitor kit.
- Fully discharge capacitors that start charging through a resistor will initially have a massive voltage change (almost 2/3) of the final voltage at the start of charging (one time constant). After that the voltage rapidly slows down how fast it rises, and it takes about 4 times as long to get to the final voltage as it took to get to that initial approx. 2/3 voltage change. Covered in more detail below.
- Same basic rules apply to a fully charged capacitor that is discharging through a resistor, but the voltage is dropping instead of rising.
Following links have a short video that cover the schematics above:
- Brief capacitor charging RC time constant demonstration circuit
- Brief capacitor discharge RC time constant circuit
Basic RC time constant properties
- One time constant ( τ / Greek letter tau) is the capacitance of the capacitor in Farads, times the resistance in ohms. τ = RC
- It takes 5 time constants to go from fully discharged to fully charged (about 99.99%) through a resistor. Also takes 5 time constants to go from fully charged to fully discharged through resistor.
- Voltage changes very rapidly during the first time constant almost 2/3 or 66% of the voltage change. and each following time constant has a much lower voltage change then the previous one. Each time constant changes almost 2/3 or 66% of the remaining voltage.
RC time constant curve diagram
Schematic diagrams used in video
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These pages are still being compiled.