A capacitor is a fundamental electronic component that stores electrical energy. It consists of two conducting plates separated by an insulating material called a dielectric. When voltage is applied, the capacitor stores energy in the electric field between the plates. This simple yet powerful device is essential in countless electronic circuits.
Every capacitor has three essential components. First, the conducting plates or electrodes, typically made of metal like aluminum or copper, which store the electrical charge. Second, the dielectric material - an insulator between the plates that can be air, ceramic, plastic, or paper. The dielectric increases the capacitor's ability to store charge. Third, the connecting terminals that provide connection points to the external circuit, allowing current to flow during charging and discharging.
During the charging process, a battery is connected across the capacitor plates. Electrons flow from the battery's negative terminal through the external circuit to one plate, creating a negative charge buildup. The other plate loses electrons to the positive terminal, becoming positively charged. This charge separation creates an electric field between the plates. The relationship between charge, capacitance, and voltage is given by Q equals C times V.
The electric field between capacitor plates is uniform and points from the positive to negative plate. The field strength equals voltage divided by plate separation distance. This electric field stores the electrical energy. The dielectric material contains molecules that align with the field, reducing its strength but increasing the capacitor's ability to store charge. The capacitance depends on the dielectric constant, plate area, and separation distance.
During discharge, the capacitor releases stored energy through an external circuit. Electrons flow from the negative plate through the load to the positive plate, neutralizing the charges. The electric field weakens as the voltage decreases exponentially. This principle is used in camera flashes for energy storage, power supplies for filtering, and RC timing circuits. The time constant tau equals R times C, determining how quickly the capacitor discharges.