Capacitance

A capacitor is formed whenever two conductors are separated by an insulator, like two charged plates which are held close together but not touching.

Capacitance plays a big factor in circuits; often for delays in circuits, energy storage (like a super short term battery), or volatile memory in computers; and components called capacitors are used to introduce capacitance in circuit designs.

The circuit symbol for a capacitor is:

Capacitors are rated in units of capacitance called "farads". Your typical capacitor in electronics in your home is \(\lt 1 mF\).

Capacitance (\(C\)), charge (\(Q\)) and voltage (\(V\)) are all related with the equation: \(Q = C \times V\)

Find the charge in a 2\(\mu\)F capacitor that has a voltage across it of 25V

Using our formula \(Q = C \times V = 2\times 10^{-6} \times 25 = 50\mu\)C Where \(\mu C\) reads "micro coulombs".

How much capacitance is required to store \(40\mu\)C of charge at a voltage of 200V?

Rearranging our formula we get \(C = \frac{Q}{V} = \frac{40 \times 10^{-6}}{200} = 200\)nF

The amount of energy stored in a capacitor is given by the equation: \(W = \frac{1}{2}CV^2\) Where \(W\) is the energy in joules, \(C\) is the capacitance in farads and \(V\) is the voltage across the capacitor in volts.