## Exploration 30.6: RC Time Constant

Please wait for the animation to completely load.

In this animation you can close and open switches to see what happens to the voltage across the capacitor **(red),** the voltage across the resistor **(green)**, and the total voltage across the capacitor plus resistor **(blue)**. Initially, the capacitor is charged. After pushing "play, " you should throw the switches **(voltage is given in volts and time is given in seconds)**. Restart.

Set the switches so that you can get a good graph of the capacitor discharging and charging.

- How much time (approximately) does it take the capacitor to charge and discharge?
- Double the battery voltage. How much time does it take to charge and discharge?
- Double the capacitance and measure the time to charge and discharge.
- Double the resistance and measure the time to charge and discharge.

The value of RC (resistance times capacitance) is the RC time constant for the circuit and is a characteristic time. Set the battery voltage to 1 V.

- When the time equals R*C after throwing the switch, what is the capacitor voltage when it is discharging? When it is charging?
- Compare your measurements to the values found from the equations for a charging or discharging capacitor:

Charging: V = V_{0} (1 - e^{ -t/RC}) Discharging: V = V_{0} e^{ -t/RC}

Exploration authored by Anne J. Cox.

Script authored by Wolfgang Christian and Anne J. Cox.