What is a capacitor? What are the functions of capacitors?

Capacitor is one of the electronic components widely used in electronic equipment, widely used in circuit isolation, coupling, bypass, filtering, tuning circuit, energy conversion, control, etc.

Capacitor, any two conductors insulated from each other and close to each other (including wires) constitute a capacitor. The general formula C=Q/U for parallel plate capacitors: the electric field strength between the plates E=U/d, capacitor capacitance determinant C=εS/4πkd, with the rapid changes in electronic information technology, digital electronic products are being updated more and more quickly, with flat-panel TVs (LCD and PDP), notebook computers, digital cameras and other products, the production and sales of consumer electronics products continue to grow, driving The growth of the capacitor industry has been driven by the continuous growth in the production and sales of consumer electronics products, mainly flat-panel TVs (LCD and PDP), notebook computers and digital cameras. China has become a global capacitor producing country.

Role

In a DC circuit, a capacitor is the equivalent of a circuit breaker. Capacitor is a component that can store electric charge and is one of the most commonly used electronic components.

This starts with the structure of a capacitor. The simplest capacitor is composed of a pole plate at both ends and an insulating dielectric (including air) in the middle. When energized, the pole plates are charged, creating a voltage (potential difference), but the entire capacitor is non-conductive because of the insulating substance in the middle. However, such a situation is under the condition that the critical voltage of the capacitor (breakdown voltage) is not exceeded. As we know, any substance is relatively insulated, and when the voltage at both ends of the substance increases to a certain level, the substance is conductive, and we call this voltage the breakdown voltage. Capacitors are no exception, capacitors are not insulators after breakdown. However, at the secondary school level, such a voltage is not seen in the circuit, so they are working below the breakdown voltage and can be treated as an insulator.

However, in AC circuits, because the direction of the current changes as a function of time. And the process of charging and discharging a capacitor is time-dependent, and at this time, a changing electric field is formed between the pole plates, and this field is also a function of time. In fact, the current passes between the capacitors in the form of an electric field.

At the secondary school level, there is a saying, which is called pass AC, block DC, referring to this property of capacitors.