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# DINGFENG CAPACITOR - - The essence of capacitors

Jun 18,2020

Let us first assume that there are two electrode plates placed parallel to A and B. The gap between them is made of insulating material such as air. Then a switch S is connected to the DC source E in the middle. When the two plates are not connected to the power supply, they are kept neutral to the uncharged state. But when the switch is turned on, the electrons of the electrode plate A are attracted to the positive electrode of the battery, so A shows a positively charged phenomenon. At the same time, the negative electrons at the negative end of the battery are repelled toward the plate B, making B appear negatively charged. Then an electric field is formed between the A and B polar plates and a potential difference V is established. This phenomenon of electron flow continues, and the amount of power transferred is proportional to the voltage of the power source. Until the potential difference between the AB plates is equal to the power supply voltage (V = E), the movement of electrons is stopped. During the flow of electrons, the energy of the power source is taken out and stored on the bipolar plate, which means that the charge is stored.

As described above, a device that has the ability to store charge by separating two parallel conductive plates with an insulating substance is called a capacitor or condenser. The electrode plate is called the electrode of the capacitor, and the insulating substance is called the dielectric or dielectric for short.

Capacitance is used to indicate the ability of a capacitor to store charge. Various capacitors have different capacitances due to factors such as the size, shape, material, distance between plates, and type of medium. However, the amount of charge Q that can be stored is proportional to its potential V, that is, Q=CV.

The proportional constant C in the formula is the capacitance of the capacitor, referred to as capacitance. C=Q/V

The unit of capacitance is "kuneng/volt". To commemorate the great contribution of scientist Faraday (Michael Faraday l791~1867, UK) to electricity, the capacitor of 1 coulomb/volt is called 1 farad. Referred to as the law, the unit symbol is F or f. In practical terms, the unit of farad is often considered too large, so the value of capacitance is often expressed in microfarad (μF) or picofarad (μμF or pF).