Capacitance Formula

Introduction

Capacitance is defined as the ability of any conductor to hold a charge. It is the ratio of the charge flowing through the conductor to the applied potential. Capacitors are the conductors for holding charges.

Capacitance is the capacity of any matter to hold an electrical charge. Any object which can be electrically charged shows capacitance. A parallel-plate capacitor is the common form of the energy storage device. Capacitance is possessed by the parallel plate combination and is described in terms of charge storage. If the capacitor is charged up totally, there is a potential difference between its plates. The larger is the area of the plates and/or the smaller is the distance between them, the bigger will be the capacitor's charge, and the bigger will be its Capacitance.

Capacitance Formula

The formula for capacitance is

Where,

• C = Capacitance (in farads, F)

• Q = Charge stored (in coulombs, C)

• V = Voltage across the conductors (in volts, V)

If capacitors are connected in series, then the formula for capacitance is given by Cs =        

       1/C1 + 1/C2 

If the capacitors are connected in parallel, the capacitance formula is given by 

       Cp = C1 + C2 

Where C1,C2,C3…….Cn are the capacitors and Capacitance is expressed in Farads 9

Solved Examples

Example 1: Determine the capacitance of the capacitor if 5 coulombs of charge is flowing when 2V of potential is applied.

Solution: Given parameters are  

                Charge Q is 5 C,

                 Applied voltage V = 2 V

Capacitance is given by

The formula:  C= Q / V 

                         = 5 / 2

                         = 2.5 F

Example 2: Calculate the capacitance if capacitors 6 F and 5 F are connected

(i) In series and

(ii) In parallel

Solution: 

The formula for capacitance in series is given as

 Cs = 1/C1 + 1/C2

       =C1+C2 / C1C2

       = 6+5 / 30

 Cs = 0.367 F

The formula for capacitance in parallel is given as

Cp = C1 + C2

= 6 + 5

Cp = 11 F

 

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