# Definition of capacitor

The capacitor is a device that stores electrical charge and electrical potential energy. The simple capacitor consists of two-conductor plates or sheets that are placed close together but do not touch each other and are separated by an insulator or a vacuum. Conductors are materials that can conduct electrical current such as metals, while insulators are materials that cannot conduct electrical current such as plastic.

At first, the two conductors are not electrically charged or electrically neutral. In order for one conductor to be positively charged and the other conductor to be negatively charged then there must be a transfer of electrons from one conductor to another. The electrons are on the surface of the atom so they are easy to move. After the electron has moved from one conductor to another, one of the conductors has an excess of electrons (lack of protons) so that it becomes negatively charged while the other conductor has an electron deficiency (excess proton) so that it becomes positively charged. A detailed description of the process of charging electric charges on capacitors is reviewed on the topic of storing electrical energy in capacitors. As illustrated in the figure beside, one of the conductor plates is positively charged (+ Q) while the other conductor plate is negatively charged (-Q). The electric charge in each plate is equal but has the opposite sign so that the total charge is zero (Q-Q = 0). The existence of an electric charge with the same size and opposite sign on each plate causes a potential difference between the two plates. The positively charged conductor has a higher electrical potential while the negatively charged conductor has a lower electrical potential. In other words, there is an electric field between the two charged conductors, where the direction of the electric field from the positive charge to the negative charge. As has been discussed in the topic of electric potential energy, if there is an electric field or a difference in electrical potential between the two conductor plates, there must be electric potential energy in the two plates.

Potential energy is the ability to do work. If the capacitor stores electrical potential energy, the capacitor has the ability to do work. As a fact, capacitors have many uses in everyday life. Capacitors are one of the important components in electrical circuits, where electrical circuits are the basis of various electronic devices. 