What is capacitor?,Capacitance of a capacitor,Series and parallel combination of capacitors,energy stored in capacitor,uses of capacitors.

Introduction

                 A capacitor consists of two conducting surfaces separated by a layer of an insulating medium called dielectric.The conducting surfaces may be in the form of either circular plates or be of spherical or cylindrical shape.

                  The purpose of a capacitor is to store electrical energy by electrostatic stress in the dielectric.

Capacitance of a Capacitor

                  The property of a capacitor to store electricity/charge may be called its capacitance.The capacitance of a capacitor is defined as the amount of charge required to create a unit potential difference between its plates.

                    If Q is the charge in coulomb to one of the two plated of a capacitor and V is the potential difference in volts between two plates then its capacitance will be 

                             

                                  C=Charge/ Potential difference

                                   C=Q/V

                So,we can define capacitance is the charge required per unit potential difference.

                 The units of capacitance is Coulomb/volt which is also called farad.

                                    1farad=1coloumb/volt

Capacitors in Series

       

        

                   We can connect capacitors in series as show in the above fig.  let,

                              C1,C2,C3=Capacitance of three capacitors

                               V1,V2,V3=P.ds across three capacitors

                                V=applied voltage across combination

                                 C=Combined or equivalent or joint capacitance

                    In series combination of the capacitors charge on all capacitors will be same where as potential difference across each is different,So

                               V=V1+V2+V3

                                Q/C=Q/C1+Q/C2+Q/C3

                                 1/C=1/C1+1/C2+1/C3

                                  Ceq=C1C2C3/C1C2+C2C3+C3C1

Capacitors in Parallel

                  When we connect capacitors in parallel as shown in the above fig.Potential difference across each is the same but charge on each is different so,

                                 Q=Q1+Q2+Q3

                                CV=C1v+C2V+C3V

                                 C+C1+C2+C3

                                  Ceq=C1+C2+C3

Energy Stored in a Capacitor

                 Charging of a capacitor always involves some expenditure of energy by the charging agency.This energy is stored in the capacitor up in the electrostatic field set up in the dielectric medium.On discharging the capacitor the field collapses and the stored energy released.

                    So,we can say energy stored in a capacitor is

                                        E=1/2 C(V)2

Uses of Capacitors

                 Capacitors are used in almost all types of electronic product in different ways.Simple way of working of capacitor is when we charged it by a current and it release that current all at once.

                 Some of the important uses of capacitors are as follows.

Energy Storage

                Capacitor can be use as an electric energy storage unit.When we connect it with charging circuit and when it is disconnected from the charging circuit it dissipate that stored energy and work like a temporary battery,So, capacitors are used in electronic devices to maintain power supply while batteries are being changed.Capacitors are used in car audio system to store energy for the amplifier.

Power Factor Correction

               Power factor correction capacitors are used for this purpose.A motor requires inductive or lagging reactive power for magnetizing.Capacitors provide capacitive or leading reactive power that cancels out the lagging reactive power when used for power factor improvement.

Capacitors for Power conditioning

                Reservoir capacitors are used in power supplies for conditioning of power supplies.Capacitors allow AC signals when they are charged they can effectively split these two signal types cleaning the supply of power.

    We can also use capacitor as

• Signal Coupling.
• Decoupling.
• Storing Energy.
• Tuning.
• High-pass and Low-pass Filters.
• Noise Filters.
• Pulsed Power and Weapons.