50)
The capacitance C, with dielectric between the plates, is then
0KA
Q
C
V
d
ε
=
=
(2 51)
 The product e0K is called the permittivity of the medium and is
denoted by e
e = e0 K
(2 52)
For vacuum K = 1 and e = e0; e0 is called the permittivity of the vacuum The dimensionless ratio
0
K
=εε
(2