Fundamentals of Electrical Engineering

Capacitor- an application

Capacitor is an electrostatic energy storage device, Capacitance depends upon the area of plates and inversely proportional to the distance between them.

C= KA/d

Types of Capacitor:

  1. Fixed Capacitor
  2. Polarised Capacitor
  3. Varying Capacitor

Capacitor Behaviour for DC & AC Supply:

For DC Circuit:

  1. In given circuit Firstly capacitor connect in series to a lamp load, when dc supply is connected to the circuit, current start to flow in circuit passage through the capacitor and lamp will be glow. Initially capacitor in charging mode so allow to flow of current whenever it is fully charged its block the current in the circuit or lamp will be off.


  1. Now we connect capacitor in parallel across the lamp load and switch on dc supply, initially capacitor start charging and current will flow in both the branch i.e. Lamp Load and Capacitor branch, its lamp will be glow in initially condition, After capacitor fully charged and works as open circuit so all the current will flow through the lamp load and it will be more glow.


For AC Circuit

  1. Capacitor allow ac signal and block dc supply(whenever it charged by dc voltage) so when its i connected in series to lamp load, lamp load will be glow and if its connected in parallel across the lamp load , lamp load will not be glow because all current pass through the capacitor branch.


Applications :

Energy Storage –  Capacitor can be store energy when it is connected to the charging circuit. Its mostly used in electronic circuit to

Filtering: when we convert AC to DC through rectification process, and get pulsating DC output waveform (some ac pulse are available)  So capacitor used in filter circuit to  remove the ac pulse in output waveform and get a pure output DC waveform.

Coupling Capacitor : Its used in RF Filter. Its allow only AC and filter DC.

Decoupling Capacitor : Its also called the BYPASS Capacitor and used in between supply and ground to reducing the noise form the circuit.

Starter :  Capacitor is used in auxiliary winding of single phase induction motor to make it self-starting. its works as a phase splitter  and help to produce the starting torque.

Power factor Improvement : Power Factor play important role in AC Circuits to control the flow of reactive power,  Capacitor is  mostly connected across the load because absorb reactive power from the circuit and help to maintain power factor near about 1, If its more less form the 1 it will increased the loss in the circuit.

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