
28-1
28.1 Theory of Capacitance
A capacitor is a system of two conducting electrodes separated by a dielectric material. e electrodes
have equal and opposite charges. e capacitance C of a capacitor is equal to the ratio of the absolute value
of th
e
ch
arge
Q to th
e
abs
olute
va
lue
of th
e
vo
ltage
be
tween
th
e
el
ectrodes,
wh
ich
ca
n
be ex
pressed
as
C
Q
V
=
(28.1)
where
C is the capacitance in farads (F)
Q is the charge in coulomb (C)
V
i
s
t
he
v
oltage
(
V)
e unit of capacitance, the farad, is a large unit; practical capacitors have capacitances in microfar-
ads
(μF or l0
−6
F), nanofarads (nF or 10
−9
F), and picofarads (pF or 10
−12
F). e conversions of