Capacitance is a circuit device made according to the capacitance effect. It maximizes the capacitance effect and gathers charges as much as possible to form a large enough electric field and store the corresponding electric field energy.

　　电容器在工程技术中应用非常广泛，它的种类、型号、规格繁多，但结构原理相同。简单来说，两个相互靠近的金属板，中间夹一层不导电的绝缘介质（如绝缘纸、云母、空气等），这就构成了电容器。

　　Capacitors are widely used in engineering technology, with various types, models and specifications, but the structure principle is the same. In short, two metal plates close to each other are sandwiched with a layer of non-conductive insulating medium (such as insulating paper, mica, air, etc.), which constitutes a capacitor.

　　当给电容器的两金属板之间施加一个电压，也就是施加一个外电场，在这个外电场的作用力下，金属板的电荷发生聚集，例如接外电压正极（电源正极）的金属板，其正电荷因受到排斥力的作用向两极板间的方向聚集，同样的，另一块金属板的负电荷也向两极板间的方向聚集。

　　When a voltage is applied between two metal plates of the capacitor, that is, an external electric field is applied. Under the force of the external electric field, the charge of the metal plate will gather. For example, the positive charge of the metal plate connected to the positive pole of the external voltage (the positive pole of the power supply) will gather in the direction between the two plates due to the repulsion force. Similarly, the negative charge of the other metal plate will also gather in the direction between the two plates.

　　有了电荷的聚集，电容器的两金属板间就建立了一个电场，即存储了一定的电场能量，这就是电容器的储能性质。一句话形容就是，电容器吸收的能量以电场能量的形式存储在极板间的电场中。

　　With the charge accumulation, an electric field is established between the two metal plates of the capacitor, that is, a certain amount of electric field energy is stored, which is the energy storage property of the capacitor. In a word, the energy absorbed by the capacitor is stored in the electric field between the plates in the form of electric field energy.

　　电容器在电路分析中的建模就是电容元件，电容元件是一种理想的元件，它仅反映了电容器能存储电荷（存储电场能量）这一物理现象，其电路符号为两条短竖线,这两条短竖线就如同两块金属板，可以说是非常形象了。

　　The modeling of capacitor in circuit analysis is the capacitor element. The capacitor element is an ideal element, which only reflects the physical phenomenon that the capacitor can store charges (store electric field energy). Its circuit symbol is two short vertical lines. These two short vertical lines are just like two metal plates, which can be said to be very visual.

　　电容器的应用非常广泛，在不同电路中发挥着不同的作用，如耦合、滤波、整流、无功补偿等。

　　Capacitors are widely used and play different roles in different circuits, such as coupling, filtering, rectification, reactive power compensation, etc.