Lab Activity: Building Circuits

Goal: To investigate the relationships between the important parameters that affect the capacitance of a parallel plate capacitor. 

Type of Activity: Structured Inquiry

Materials Needed:  One 9-volt battery, one 20000-Ohm resistor, one 1000-microfarad capacitor, connector wires, a stopwatch, a circuit simulator

Activity:
Part 1:
Build the circuit shown below. NOTE: If the type of capacitor you use has a positive and a negative side it's called an electrolytic capacitor. The dielectric in such capacitors is very thin, and is created in the manufacturing process by having an insulation layer produced by electrolytic deposition. If the polarity of the capacitor is not connected correctly to the potential difference, the thin layer can be destroyed, allowing conduction through the capacitor (dielectric breakdown) and overheating. So when making your connections, be sure that the positive lead on the capacitor is attached to the high potential and the negative lead is attached to the low potential. In other words, if connecting directly to a battery, the positive side of the capacitor connects to the positive side of the battery. If your capacitor does not have positive and negative markings, then there is no need to worry about this.

IMPORTANT: Make sure that the capacitor is fully discharged before connecting it in the circuit in parts C and D. This can be done by simply connecting a single wire across the capacitor (short-circuit it).

A. Do not connect to one pole of the battery until you are ready to take measurements. The unconnected wire will act as a switch.
B. Calculate and record the time constant (RC).
C. Use a stopwatch and a multimeter (in voltmeter mode) to record the voltage across the capacitor every 5 seconds after you make the final connection to the battery until the system reaches steady state. Record your results in a data table.
D. Repeat step C, this time measuring the voltage across the resistor.
E. Create two graphs. On the first graph show the voltage across the capacitor versus time and on the second graph show voltage across the resistor versus time. Discuss the relationship between the two graphs in the conclusion of your lab report.

Part 2:
Work out the answers (by hand) for activity #2 shown below. Use the simulation to build the circuit and test your answers.


Use the simulation to build the circuit and test your answers. After the simulation opens, choose the RLC option and then build the circuit seen above. Use the simulation meters to measure the answers you previously calculated by hand. Verify that your answers match those given by the solution. If they differ, explain why.