RP9-Charging and discharging capacitors

• Equipment: Capacitor, resistor, battery, voltmeter, switch, power supply.
• Charging set up: set up the power supply, switch, resistor and capacitor in series and connect a voltmeter in parallel across the capacitor.
• Charging method: Close the switch and record the voltage reading in five second intervals for two minutes. Repeat the experiment twice more and calculate a mean voltage for each time period.
• Charging graph: Plot a graph of V against t. It will show an exponential growth curve.
• Charging analysis: V = V0 (1 - e^ -t/RC). The time constant can be found by finding t when the voltage is 63 % of the maximum voltage.
• Discharging set up: Set up a capacitor with a two pole switch connected in series with either a power supply or a resistor. A voltmeter should be placed in parallel on the side with the resistor.
• Discharging method: Use the switch to connect the capacitor to the power supply until fully charged. Move the switch to connect it to the resistor and voltmeter and record the voltage in five second intervals for two minutes.
• Discharging graph: Plot a graph of ln(V/V0) against t. This will produce a straight line graph with a gradient of -1/RC.
• Discharging analysis: V = V0 e ^ -t/RC. ln(V/V0) = -t/RC.
• Safety: Capacitors can explode and release harmful chemicals - ensure the capacitor is connected in the correct polarity and that the voltage of the power supply doesn't exceed the voltage rating.