electricity electrical circuits electrical components capacitance Purpose of the experiment Determine the capacitance of the capacitor, if the voltage across the plates of the capacitor is monitored while it charges or discharges and a curve is fitted to the resulting U vs. t plot. back It is better to select a capacitor which capacitance is bigger then 1 mF. A capacitor like this charges and discharges within a few seconds with the chosen 1 kW resistor. Example e-ProLab file of the capacitor charging Example e-ProLab file of the capacitor discharging Example curve of the capacitor charging Example curve of the capacitor discharging The data table of charging the capacitor The data table of discharging the capacitor back Instructions for data analysis Students can determine the capacitance of the capacitor C from the curve of discharging a capacitor e.g. As we can see from the chart of voltage vs. time, the fitted exponential function is From theory where R = 2200 W. The capacitance is approximately back Conclusions When the capacitor is discharged through a resistor, the voltage across the capacitor and the charge on the capacitor decreases exponentially. When the capacitor is charged through a resistor, the voltage exponentially rises. Student activities Investigate to see how the U vs. t plot changes when the values for R and C are changed. Explain the results obtained. Additional activities To express the units of resistance, ohms, and the units of capacitance, farads, in fundamental units. back Related experiments