What is a Capacitor?

A Capacitor is a device for storing electric charges.  When two parallel plates of dielectric material are made to pass a voltage, it stores electric charge. The main thing is two parallel plates should be of dielectric material.

The unit of capacitance is farad. Mu farad and Pico farad is the most commonly used format for representation.

The effect of capacitance can also be seen in a transmission line. There would be a capacitance between the transmission lines. Here the transmission line acts as a dielectric. In the phase R, Y, B the capacitance effect would be present between RY and YB.


Classification of Capacitors:

According to the variability in value, the capacitors are classified into two.

Variable Capacitors:

Their value can be varied within the definite limit.

Example: Decade Capacitance Box

The variable capacitors are most commonly used in tuning circuits, where there is a compulsory need to change frequency.

Non-Variable Capacitors:

Their value cannot be varied.

Example: A normal capacitor

The non-variable capacitors are most commonly used in electronic circuits for smooth charging and smooth discharging.

One can use both variable capacitance and non-variable capacitance for the same operation, but the drawback is if you are going to use a variable capacitor, the size of the circuit becomes bulk. But in tuning circuits, we need to change the frequency manually. So it would be more convenient to use the variable capacitors.

Besides these, there were many different types of capacitors used in practice.


  1. In Low Pass filter, High Pass filter, Band Pass filter.
  2. In charging circuits.
  3. In Power systems, to increase the efficiency of transmission.
  4. In Ignition system of Automobile Engines to eliminate sparking.
  5. In generating electromagnetic Oscillations and so on.


  1.   Due to aging, the performance will decrease.
  2.  Size will increase for a higher rating.





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