Capacitors

Ever wondered what a capacitor is and what it is used for?
A capacitor is simply two conductors that are separated by an insulator. The two conductors usually carry an equal and opposite charge such that total charge on the capacitor as a whole is zero. A capacitor is an electrical device that stores electric charge.
 
Charging and discharging a capacitor
Let's imagine a capacitor with two plates A and B. When a capacitor is connected to a battery, electrons flow from the negative pole of the battery on to plate A of the capacitor. At the same rate, electrons flow from the plate B of the capacitor towards the positive terminal of the battery. Positive and negative charges thus appear on the  plates. As the charges accumulates, the potential difference between A and B increases and the charging current reduces to zero when the potential difference becomes equal to the battery voltage.
When the battery is disconnected, the capacitor stays fully charged. To discharge the capacitor, the plates are joined with a thick wire and electrons flow from plate A to plate B until the positive charge on B is completely neutralized. A current thus flows for a time in the wire and at the end of time, the  charges on the plate becomes zero.
The ability of the capacitor to store charge is called the capacitance of capacitor and the unit is farad.

Uses of capacitor
Capacitors have many uses in electrical circuits. They are,
- Tuning in radio circuits
- Smoothening rectified current from DC suppliers
- Elimination of sparking in switches
- Storage of large quantities of charge
- Blocking of noise in an ac amplifier