The capacitance of a capacitor is defined as the ratio of the charge in one of the plates to the potential difference between the plates. The next formulas are used to make calculations involving capacitances.
Formula 1
C = Q / V
Where:
C is the capacitance in farads (F)
Q is the amount of charge in one plate in coulombs ( C )
V is the voltage between plates in volts (V)
Note: If the capacitance is expressed in ?F the charge will be found in ?C or, if the capacitance is expressed in pF the charge will be found in pC (keeping the voltage em volts).
Derivated Formulas:
Formula 2
Q = C x V
Formula 3
V = Q / C
Application example:
Calculate the amount of charge stored in a 100 µF capacitor when the potential difference between plates is 100 volts..
Data:
C = 100 µF ou 100 x 10-6 F
V = 100 V
Q = ?
Applying formula 2:
Q = 100 x 10-6 x 100 = 104 x 10-6 = 10-2 C = 10 000 µC
