In the realm of electrical engineering, a capacitor is a two-terminal electrical device that stores electrical energy by collecting electric charges on two closely spaced surfaces, which are insulated from each other. The area between the conductors can be filled with either a vacuum or an insulating material called a dielectric.
Capacitance tells us how much electrical charge a capacitor can store per unit of voltage. It quantifies the ability of a capacitor to hold and release energy. In simpler terms, it measures the “size” of a capacitor’s storage tank for electrical charge. The capacitance of a capacitor is measured in a unit called the farad.
One of the most common applications of capacitors in large buildings is for power factor correction. When too many inductive loads are placed into a circuit, the current and voltage waveforms will fall out of sync with each other and the current will lag behind the voltage.
Capacitors are rated by using a number of different values. Capacitance, voltage level, tolerance, leakage current, temperature tolerances are all different ways a capacitor is spec’d. When selecting a capacitor for a task it must match the required voltage / current levels.
Unlike a resistor, capacitors do not dissipate energy – they do the opposite and store it. Capacitors are two-terminal passive components that are used in the majority of electrical circuits and systems that you come across. What makes capacitors so useful and stand out from other components is their ability to store energy.
A practical capacitor is a type of capacitor that consists of two sets of semicircular aluminum or brass plates separated by a dielectric material. Practical capacitors can be constructed by interleaving the plates with two dielectric layers and rolling them up.