What Is a Capacitor?

Two adjacent conductors are sandwiched by a layer of non-conductive insulating medium to form a capacitor. When a voltage is applied between two plates of a capacitor, the capacitor stores charge. The capacitance of a capacitor is numerically equal to the ratio of the amount of charge on one conductive electrode plate to the voltage between two electrode plates. The basic unit of capacitance of a capacitor is farad (F). The capacitor element is usually represented by the letter C in the circuit diagram. ^[1]

Capacitors are components that store electricity and electrical energy (potential energy). A conductor is surrounded by another conductor, or the electric field lines emitted by one conductor all terminate in the conduction system of the other conductor, which is called a capacitor. ^[3]

(1) Nominal capacitance is the capacitance marked on the capacitor. But the actual capacitance of the capacitor is

According to analysis statistics, capacitors are mainly divided into the following 10 categories:

1. Divided into three categories according to structure: fixed capacitors, variable capacitors and trimmer capacitors. ^[6]

1. Detect small capacitors below 10pF: Because the capacity of fixed capacitors below 10pF is too small, use a multimeter to measure it. Only qualitatively check for leakage, internal short circuit or breakdown. When measuring, you can choose a multimeter R × 10k block. Use two test leads to connect the two pins of the capacitor at will. The resistance should be infinite. If the measured resistance value (the pointer swings to the right) is zero, it means that the capacitor leakage is damaged or internal breakdown. ^[12]

(1) The charging process.

The process of charging a capacitor (storage charge and electrical energy) is called charging. One pole of the capacitor is connected to the positive pole of the power source, and the other pole is connected to the negative pole of the power source. The two pole plates are respectively charged with the same amount of heterogeneous charges. After charging, there is an electric field between the two plates of the capacitor, and the charging process stores the electric energy obtained from the power source in the capacitor. ^[13]

1. Common failures of capacitors. Turn off the power immediately when one of the following conditions of the capacitor is found. ^[14]

Supercapacitors, also known as electric double layer capacitors and electrochemical capacitors, are a new type of electrochemical energy storage device with electrochemical performance that is between traditional capacitors and batteries. It mainly stores energy through electric double-layer capacitors and Faraday quasi-capacitors produced by redox reactions. Generally speaking, the energy storage method of supercapacitors is reversible, so it can be used to solve problems such as battery memory. At present, the application scope of supercapacitors is very wide, especially in the field of hybrid electric vehicles. As a power source of a hybrid vehicle, it can well meet the high power requirements of the car during startup, hill climbing and acceleration, thereby effectively saving energy and increasing the battery life. ^[16]

For supercapacitors, there are different classification methods based on different contents. First, according to different energy storage mechanisms, supercapacitors can be divided into two categories: electric double layer capacitors and Faraday quasi capacitors. Among them, electric double-layer capacitors generate storage energy mainly through the adsorption of pure electrostatic charges on the electrode surface. Faraday quasi-capacitors mainly generate Faraday quasi-capacitance through reversible redox reactions on and near the surface of Faraday quasi-capacitive active electrode materials (such as transition metal oxides and polymer polymers), thereby achieving energy storage and conversion. Secondly, according to the type of electrolyte, it can be divided into two categories: aqueous supercapacitors and organic supercapacitors. In addition, depending on whether the types of active materials are the same, they can be divided into symmetric supercapacitors and asymmetric supercapacitors. Finally, according to the state of the electrolyte, supercapacitors can be divided into two categories: solid electrolyte supercapacitors and liquid electrolyte supercapacitors. ^[16]