Mon. Week 9, April 21: Capacitance

This day's main topic of discussion was on the subject of capacitance, and the capacitor. The simple definition of capacitance is the potential difference between two conductors separated by an insulator. The charge on each conductor is opposite in polarity and the two charges remain stationary since they are attracted to each other through the insulator via their electric fields. The official definition of capacitance is the ratio of charge on each conductor and the potential difference across them.

The first exercise of the day was a derivation of the definition of capacitance as a function of the conductors' surface area and length of separation. It was found that capacitance is directly proportional to the surface area of the conductors and inversely proportional to the amount of distance between each conductor.

We then started an experiment to verify this proportionality of capacitance and surface area/distance. The experiment consisted of taking two sheets of conductive material (aluminum foil) and using a multimeter to measure the capacitance of the two sheets as the distance between them was increased and the surface area  was decreased.

The gathered data verified the results predicted from the derivation we made at the start of class. As distance increased, the capacitance decreased, and as surface area decreased, the capacitance decreased.

The next segment of class was an introduction to the capacitor. The capacitor is a circuit component that is capable of storing energy in the form of an electric field. 
One of the most important concepts to know on the topic of capacitors is equivalent capacitance. Much like resistors, the capacitance of a variety of capacitors in a circuit can be replaced by an equivalent capacitance based on whether the capacitors are hooked up in series or a parallel configuration.

We learned that capacitors in parallel are summed up, while capacitors in series are summed inversely, the opposite of combining resistors. We verified this by measuring the capacitance of capacitors in parallel and series.