Capacitors are components that can store energy in an electrical field. They are one of the most basic electrical components and can be found in almost all electrical devices. Capacitance is measured in Farads (F), but we mostly deal with smaller values such as 1 mF (millifarad) or 1 μF (microfarad).
Applications
When we have a voltage difference across a capacitor, electrons will gather and build up a negative charge in the capacitor. When the voltage difference disappears, these electrons will seep out again flow into the circuit until the capacitor is at equilibrium again. This effect can be useful to provide momentary energy during a brief power shortage or to smooth out a signal that fluctuates.
To understand how much power might be stored in a capacitor we first need a unit of charge. One Coulomb is a unit of a charge equivalent to that transported by 1 ampere in 1 second.
One Farad is equal to one coulomb when we have an applied voltage drop of 1 volt. In other words, a one-farad capacitor will hold 1 amp-second of electrons at 1 volt, or 0.2 amp-seconds at 5 volts.
F = C/V