## Capacitors and Discharging

Last week, we talked about Gauss's law. In the project you found the electric field and electric potential between two parallel sheets of charge. If we increase the amount of charge on the plate - E-field and voltage would increase. These notes will talk about the ratio of charge to voltage, called capacitance, and what would happen if you connect a conducting wire between the plates.

### Capacitance

Capacitance is defined as the ratio of…stuffs. Equations and fun times…

#### Capacitance for Parallel Plates

Starting from Gauss's law…only depends on area of plates and separation. Depends on geometry, capacitance is constant - defines ratio again.

### Discharging a Capacitor

What happens if we connect plates with a conducting wire? Excess electrons travel to positive plate - happens quickly at first b/c lots of repelling and strong attraction, happens more slowly as time goes on. Exponential decay of excess charge. (Corresponds to decay of electric potential.) Equilibrium definition.

### Energy and Charge Storage

Separation of charge = energy storage. Capacitors let you store charge, store energy.

### Examples

Capacitance for cylinders