A capacitor is a device for storing charge. It is usually made up of two plates separated by a thin insulating material known as the dielectric. One plate of the capacitor is positively charged, while the other has negative charge. While
A Power bank is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.
- Power bank store energy and so do capacitors. However, the principles are much different, and batteries can store much more energy.
- Power bank actually store chemical energy. One can make a battery, for example, by placing a piece of zinc and a piece of carbon (such as the graphite in a lead pencil) into a lemon (which serves as an electrolyte). The battery will work until the zinc has been used up (providing the electrolyte has not dried out). However the battery is made, the total energy E that it can produce is the voltage V of the battery multiplied by the current I it produces multiplied by the time t. (E = VIt) The product It is the total amount of electric charge Q that moves through the wires when electric current flows, to the energy is E = VQ.
- Capacitors are very good at storing charge for short time periods, and they can be charged and recharged very quickly. There are many applications, however, where it’s more convenient to have a slow-but-steady flow of charge; for these applications batteries are used.
- In a capacitor, the energy comes from the fact that the stored charge on one plate repels like charge on the same plate and attracts unlike charge on the other. When an external circuit is provided, the charge flows from one plate to the other, each tending to neutralize the other. If half the charge becomes neutralized, the voltage is half of its starting value. (In a battery, the voltage remains constant instead.) In terms of the charge Q stored on the capacitor and the starting voltage V, the energy E = (1/2)
Types of capacitor
- Polypropylene capacitor: The polypropylene capacitor is sometimes used when a higher tolerance type of capacitor is necessary than polyester capacitors offer. As the name implies, this capacitor uses a polypropylene film for the dielectric. One of the advantages of the capacitor is that there is very little change of capacitance with time and voltage applied. This type of capacitor is also used for low frequencies, with 100 kHz or so being the upper limit. They are generally only available as leaded electronics components.
- Glass capacitors: As the name implies, this capacitor type uses glass as the dielectric. Although expensive, these capacitors offer very high levels or performance in terms of extremely low loss, high RF current capability, no piezo-electric noise and other features making them ideal for many performance RF applications.
- Supercap: Also known as a supercapacitor or ultracapacitor, as the name implies these capacitors have very large values of capacitance, of up to several thousand Farads. They find uses for providing a memory hold-up supply and also within automotive applications.