Working of Capacitor

Actually the capacitor is nothing but an electronic component, it is very much similar to battery. The common thing that the Battery and Capacitor do is both of them store electrical energy. We know that battery consist of two terminal. In which chemical reactions produce electrons on one terminal and absorb electrons at the other terminal.
               But a capacitor do not produce new electron, it only stores the electron. Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect to two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or anything else that does not conduct electricity and keeps the plates from touching each other.

The symbol of capacitor is as shown below in the figure,

We use battery usually in a small circuit, so in the figure below we have connected a Capacitor to a Battery.

• The plate on the capacitor that attaches to the negative terminal of the battery acceptselectrons that the battery is producing.

• The plate on the capacitor that attaches to the positive terminal of the battery loses electrons tothe battery.
  
  Once it's charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor). For a small capacitor, the capacity is small. But large capacitors can hold quite a bit of charge. You can find capacitors as big as soda cans, for example, that hold enough charge to light a flashlight bulb for a minute or more. When you see lightning in the sky, what you are seeing is a huge capacitor where one plate is the cloud and the other plate is the ground, and the lightning is the charge releasing between these two "plates." Obviously, in a capacitor that large, you can hold a huge amount of charge!
  
  
  Lets do small experiment to understand working of capacitor.
  
  
  
  Here you have a battery, a light bulb and a capacitor. If the capacitor is pretty big, what you would notice is that, when you connected the battery, the light bulb would light up as current flows from the battery to the capacitor to charge it up. The bulb would get progressively dimmer and finally go out once the capacitor reached its capacity. Then you could remove the battery and replace it with a wire. Current would flow from one plate of the capacitor to the other. The light bulb would light and then get dimmer and dimmer, finally going out once the capacitor had completely discharged (the same number of electrons on both plates).

Further explanation about its units(FARAD) and application is discussed in other blogs