### How a capacitor works

This video lesson explains how a capacitor can store a small amount of electrical energy and why this is useful. They do this by holding a charge between two thin sheets of metal held very close together. The value of the capacitance depends upon the area of the sheets, which are rolled up with thin layers of insulation in between them. That thin layer of insulation, usually made of either paper, a plastic film or simply an oxide layer on the surface of the metal. The video uses practical demonstration and simulations to explain how that can be done in practice by making a simple example.

Illustrated notes are here

### Capacitors in series and parallel and the time constant

As in the title the video lesson explains how arranging capacitors in series and then in parallel changes the total value. Briefly when they are in parallel the total capacitance is the the simple addition of the individual values. When in series the total capacitance is less than the smallest single value. The video explains how to work this out.

The second part of the video shows how a combination with a resistor provides a well known arrangement that can be used as a timer. The video shows the pattern in change of voltage and current as the combination is charged or discharged, how this is measured and then how we use the idea of the time constant.

The range of video lessons available on flash drive is described here