Most capacitors can be classified as electrolytic, ceramic, or supercapacitors. Ceramic capacitors are made of ceramic materials. They are cheap and small are applied in high frequency circuits Their capacitance can change with voltage variations. Electrolytic capacitors are usually much bigger in size and have larger capacitances. Capacitances are measured in a unit called Farad. Actual capacitors have much smaller values called micro-farad (uF) and pico-farad (pF)
Capacitors are connected in series when positive to negative connections are joined. In series, the capacitance of each capacitor is now the inverse of its capacitance. The series then has a total capacitance smaller than the sum of the unconnected capacitances. Capacitors are connected in parallel when all the positives are connected to a point and all the negatives connected to another point. In the parallel connection, the capacitances directly add up.
Capacitors are charged when connected to a Direct Current, DC, source, reaching a maximum value after some time, and maintains the charge as long as the supply voltage is present. However, when a capacitor is subjected to an Alternating Current, AC, it behaves differently. It will get charged and discharged depending on the frequency of the AC. This AC property of capacitors finds application in circuits that have resistance and inductance to create sinusoidal waves.
Capacitors can store large quantities of electrical charge and energy, making them useful in many environments. For example, they can act as temporary battery in electronic devices while changing batteries. Most Uninterruptible Power Systems (UPS systems) in use today consist of high storage capacitors in parallel. Power conditioning equipments use capacitors and they are also used in electronic devices such as cameras and computers. In car radio systems, capacitors store energy that becomes useful in the amplifier. Large banks of high storage capacitors are used to denote and explode nuclear weapons. Also power supply systems all use high voltage capacitors in their design. Model electric cars in operation use banks of rechargeable capacitors as energy source.