What are capacitors and how do they work?

Question

What are capacitors and how do they work? Please explain in a simple way.

Answer 1

capacitor is a device used to store charge.

it stores charge between their parallel plates in the presence of electric field.



they can also be used as temprory battery.

it also works to allow ac signal but does not allow to flow dc current.

Answer 2

at the simplest a capacitor is 2 conductive plates separated by a thin layer of an dielectric material. A dielectric material is an insulator which can align itself with an electric field. when the dielectric aligns with an electric field that causes a charge difference along the electric field- and for a capacitor that means each plate has equal and opposite charges. Any charge difference is a voltage potential. Applying an external voltage(that's greater than that already across a capacitor) will increase the electric field inside the capacitor.

the stronger the dielectric value, the thinner the dielectric, and the more plate area the stronger the capacitor.



C=εr*ε0*A/d

C is the capacitance;

A is the area of overlap of the two plates;

εr is the relative static permittivity (sometimes called the dielectric constant) of the material between the plates (for a vacuum, εr = 1);

ε0 is the electric constant (ε0 ≈ 8.854×10−12 F m–1); and

d is the separation between the plates.



The dielectric material doesn't need to be plastic- I've found titanium dioxide produced by anodizing titanium is capable of produce pretty strong capacitors.Probably because it's a strong insulator, and it can be a very thin (which also increases capacitance), eg http://stevebb.wordpress.com/home/water-variable-polarised-capacitor/

Answer 3

You Have all the answers what is a capacitor is in the above answers but no works, Basically if a capacitor is connected to a battery positive potential to one plate negative to the other. electrons being negatively charged ,will leave the positively connect plate and flow to the negatively connected plate and the electron will flow until the negatively plate reaches the fully charged condition repelling any further electron flow and is said to have blocked the direct current.AS for AC as the plates are changing polarity every half cycle the current flow first one way and then the other way charging and discharging the capacitor an AC current appears both sides of the capacitor enabling a capacitor to pass an AC current

Answer 4

A capacitor consists of 2 plates with a dielectric between them. The dielectric is an insulator, to there can be no DC current. However, caps can be charged by an AC current. When a cap is charged, energy is stored in the electric field between the plates.

Answer 5

DEFINITION-Capacitor is a simple electronic device that is used to store electrical energy. They are only used to store the electrons and they are not capable of producing them. Previously in old TV sets or Radio you would find them as cylidrical (ceramic or myca) with 2 legs with uF (micro Farad sign) You can also see them attached to Table fans in cylindrical white color. Due to Microelectronics size has shruck n Now they come in IC (chip) form embedded in electroic MCB of TV/Remote/Computer/Mobile every electronic item.



STRUCTURE- capacitor consists of two metal plates which are separated by a non-conducting substance or dielectric. (eg porcelain (ceramic), mica, glass, plastics, and the oxides of various metals) Dielectric is poor conductor of electricity, but an efficient supporter of electrostatic fields.



WORKING of capacitor

Though any non-conducting substance can be used as a dielectric, practically some special materials like porcelain, mylar, teflon, mica, cellulose and so on. A capacitor is defined by the type of dielecric selected. It also defines the application of the capacitor.

According to the size and type of dielectric used, the capacitor can be used for high-voltage as well as low-voltage applications.

For applications in radio tuning circuits air is commonly used as the dielectric. for applications in timer circuits mylar is used as the dielectric. For high voltage applications glass is normally used. For application in X-ray and MRI machines, ceramic is mostly preferred.

The metal plates are separated by a distance “d”, and a dielectric material is placed in-between the plates.

The dielectric constant of the dielectric material = e0e………………e0 is the dielectric of air.

The dielectric material is the main substance that helps in storing the electrical energy.

Definition of Capacitance

There are mainly two concepts for defining capacitance.

ELECTRICAL concept -

Capacitance is said to be the capacitor’s storage potential. In other words, for an existing potential difference or voltage “V” across the plates, the capacitance is said to be the amount of charge “Q” stored in between the plates.

Capacitance, C = Q/V



PHYSICAL concept - capacitance is defined by the physical characteristics of the two plates, such that the capacitance is equal to the ratio between the square area of a plate and the distance between the plates multiplied by the dielectric of the material in between the plates

Capacitance, C = e0e A/d



The capacitance is measured in Farads.

A capacitor is said to have 1 Farad of capacitance when the capacitor can hold 1 amp-second of electrons at 1 volt at a rate of electron flow of 1 coulomb of electrons per second. As 1 Farad is a big value, the capacitors are usually denoted in micro farads.



Advantages

Since the capacitor can discharge in a fraction of a second, it has a very large advantage. Capacitors are used for appliances which require high speed use like in camera flash and laser techniques.

Capacitors are used to remove ripples by removing the peaks and filling in the valleys.

A capacitor allows ac voltage to pass through and blocks dc voltage. This has been used in many electronic applications eg Inverter used in homes.



You may also see following links on youtube



http://youtu.be/riZkGSXZ7JE



http://www.youtube.com/watch?v=ORW7Qr4Nhtk



rgards



Manish Nagpal

ECE Graduate.

Answer 6

i know that they contain pieces of foil that hold charge with an insulator (plastic) inbetween the foil. the idea is that a capacitor stores charge, but releases it much faster than a battery. sorry if this isnt detailed enough!