Capacitors

Capacitors

Capacitors or condensers (a passive electronic component) consist of a pair of metal plates (conductors) separated by a dielectric (insulator). When connected to a power supply (making a potential difference) a static electric field develops in the dielectric that stores energy and produces a mechanical force between the conductors. The unit of capacitance is the farad but because we only use a very small amount of farads they are commonly known as micro farads. This is a ratio of electrical charge on each conductor, to the potential difference between them.

 Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies and for many other purposes.

The effect is greatest when there is a narrow separation between large areas of conductor; hence capacitor conductors are often called "plates". In practice the dielectric between the plates passes a small amount of leakage current and also has an electric field strength limit, resulting in a breakdown voltage, while the conductors and leads introduce an equivalent series resistance.

Capacitor Charging Circuit

This Exercise displays how capacitors charge in relation to the resistance and Frauds of the resistor and capacitor in the circuit (pictured). The time to charge is first calculated by 

T(ms) = C(uF)*R(K)*5.

 Next the circuit is created and reading are observed and graphed (pictured) for example circuit number 1 uses a 12V supply, 100uF capacitor(C) and a 1K resistor. The calculated time is 5 second but the observed is 2.5 second. It can be concluded from the four graphs (and confirmed from the calculated data) that as resistance increased the charge time also increased, also that when the capacitor size is increased to 330uF the charge time increased proportionally.