What is the Unit of Capacitance ?

The constant of proportionality has units of coulombs per volt, or Farad (F) after the English Physicist MICHAEL FARADAY.

• The Farad is the capacitance of a capacitor that contains a charge of 1 coulomb when the potential difference between its terminals is 1 volts.

• A typical capacitor has capacitance measured in microfarads (µF).

• A full farad of capacitance is theoretically possible, but it is not the usual circuit component.

• Capacitors cover the practical range from a few picofarads (pF) to thousands of microfarads (µF). A picofarad (pF) is one millionth of a microfarad.

Shapes of the Capacitor

• Capacitors are passive elements.

• They come in many shapes and forms, one of which is a foil capacitor.

• It is made from layers of metallized paper separated by insulators rolled into cylindrical shapes.

• Smaller capacitors are often just layers of metallized dielectrics.

• A basic capacitor is a version of Figure 12.1.

Figure 12.1 A Capacitor

The factors that determine the capacitance of a capacitor are:

1. The area of the plates
2. The distance between the plates
3. the type of the dielectric material used

The capacitance of a capacitor is directly proportional to the surface area of the plates and inversely proportional to the distance between them.