Capacitance | Definition | Unit | Formula

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Electrical Capacitance of A Conductor-


The electrical capacitance of a conductor is a measure of its ability to store electric charge or energy.


It is a positive scalar quantity.


Capacitance Formula-


When a conductor is given some charge, it acquires a certain electric potential.

More is the charge on a conductor, more is the electric potential of it.


If a charge Q is put on a conductor which raises its potential by V, then-

Or we can write-


where C is a constant of proportionality called as electrical capacitance of the conductor.


From here, we have-




If V = 1 unit, then C = Q. Thus,


The electrical capacitance of a conductor may be defined as the charge required to raise its potential by a unit amount.


Factors Affecting Capacitance-


The capacitance of a conductor depends upon the following factors-

  • shape and size of the conductor
  • nature (permittivity) of the surrounding medium
  • presence of the other conductors in its neighborhood


It is worth noticing that the capacitance of a conductor does not depend on the-

  • nature of material of the conductor
  • amount of charge existing on the conductor


SI Unit of Capacitance-


The SI unit of capacitance is farad (F).


1 F = 1 C V-1

The capacitance of conductor is said to be one farad if one coulomb of charge is required to raise its potential by 1 volt.


It is important to note that one farad is a very large unit of capacitance. Other smaller and practical units of capacitance are-

  • 1 micro farad (μF) = 10-6 F
  • 1 nano farad (nF) = 10-9 F
  • 1 pico farad (pF or μμF) = 10-12 F


Dimensional Formula of Capacitance-


The dimensional formula of capacitance is [M-1L-2T4A2].


It can be derived as-



Also Read- Deriving Dimensional Formula of Electric Potential


Read the next article on-

Capacitance of Isolated Spherical Conductor


Get more notes & other study material of the Chapter Electrostatic Potential & Capacitance.

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