Theoretical introduction

Capacitance is the ability to hold an electric field. Any electrostatic field is composed of many capacitors, there is an electrostatic field there is a capacitor, capacitor is described by electrostatic field. It is generally believed that an isolated conductor and infinity constitute a capacitor, and a conductor grounded is equivalent to being connected to infinity and connected to the earth as a whole.

Practical application

A variety of capacitors are used in electronics manufacturing,

They each play a different role in the circuit. As the name suggests, a capacitor is a "container that stores electrical charge." Although there are many varieties of capacitors, their basic structure and principle are the same. A capacitor is formed when two pieces of metal close together are separated by a substance (solid, gas or liquid). The two pieces of metal are called plates, and the material in between is called the medium. Capacitors are also divided into fixed capacity and variable capacity. However, it is common to use fixed capacity capacitors, and the most common are electrolytic capacitors and ceramic capacitors.

Different capacitors have different capacities to store charge. The amount of charge stored when the capacitor is applied with 1 volt DC voltage is called the capacitance of the capacitor.

In electronic circuits, capacitors are used to block direct current through alternating current, and also to store and release electrical charges to act as filters to smooth out pulsating output signals. Small capacity capacitors, commonly used in high-frequency circuits such as radios, transmitters, and oscillators. Large capacity capacitors are often used for filtering and storing charges. And there is another feature, generally more than 1μF capacitors are electrolytic capacitors, and the capacitors below 1μF are mostly ceramic capacitors, of course, there are others, such as: monolithic capacitors, polyester capacitors, small-capacity mica capacitors, etc. Electrolytic capacitors have an aluminum shell, which is filled with electrolyte, and lead to two electrodes, as positive (+), negative (-) poles, unlike other capacitors, their polarity in the circuit can not be wrong, and other capacitors have no polarity.

The two electrodes of the capacitor are connected to the positive and negative terminals of the power supply, and after a while, even if the power supply is disconnected, there will still be residual voltage between the two pins, and the capacitor stores charge. The voltage between the capacitor plates is established and the electrical energy is accumulated, which is called the charging of the capacitor. A fully charged capacitor has a certain voltage at both ends. The process by which the charge stored in a capacitor is released to a circuit is called discharge of a capacitor.

In the electronic circuit, only in the capacitor charging process, there is current flow, after the end of the charging process, the capacitor is not through the direct current, in the circuit plays the role of "DC isolation". In the circuit, the capacitor is often used as a coupling, bypass, filter, etc., which is the use of its "AC, separate DC" characteristics. Alternating current not only changes in direction, but also changes in size according to the law. The capacitor is connected to the AC power supply, and the capacitor continuously charges and discharges, and the charging current and discharge current that flow through the circuit are consistent with the change law of the AC power (different phase).

The selection of capacitors involves many problems. The first is the problem of pressure resistance. The voltage applied to both ends of a capacitor exceeds its rated voltage, and the capacitor will be damaged by breakdown. General electrolytic capacitor voltage range is Φ6.3V, Φ10V, Φ16V, Φ25V, Φ50V and so on.

Capacitive action

The basic function of the capacitor is to prevent the direct current communication; Charge and discharge.

However, many circuit phenomena that extend from this basic role make capacitors have various uses, such as: in electric motors, they are used to produce phase shifts; In a photographic flash, it is used to produce a high energy instantaneous discharge. In the filter circuit it is the main. Capacitors of different nature of the use of many, although there are many different uses, but because of its role are from charging and discharging. And its nature of blocking direct communication.