RC Circuit Experiment
1. Set up three different RC circuits using the components supplied.
2. Measure the voltage across the capacitor as a function of time using the
Pasco voltage sensor.
3. Do a best fit for your V vs. t plot for RC charging.
4. Use your best fit to determine the experimental time constant of the circuit.
Compare this value with the theoretical time constant using a percent error.
Circuit 1:
R = 10kW
C = 470mF
Circuit 2:
R = 470kW
with two 47mF capacitors in series
Circuit 3:
R = 470kW
with two 47mF capacitors in parallel
Questions
1. Show using V(t) = Vmax(1-e-t/t) , that the time required for the capacitor
to charge to ½ of the maximum voltage is tln(2).
2. For discharging, the theoretical expression is V(t) = Voe-t/RC .
If one time constant has passed, show that V = 37% Vo .
Circuit 1:
R = 10kW
C = 470mF
Circuit 2:
R = 470kW
with two 47mF capacitors in series
Circuit 3:
R = 470kW
with two 47mF capacitors in parallel
Report Items
1. A best fit equation for each circuit for RC charging.
2. An experimental time constant from each best fit
equation.
3. A theoretical constant for each circuit with
a percent error between the experimental and
theoretical t.
4. Questions 1 and 2.
5. Summary