الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

C
Q
ο ο
ο
= = = κ
(6.20)
V
d
V
Q
ο
κ
Q
V
ο
Lectures in General Physics
For a parallel plate capacitor with dielectric we can write the capacitance.
ε ο
A
C = κ
(6.21)
d
Example 6.10
A parallel plate capacitor of area A and separation d is connected to a
battery to charge the capacitor to potential difference V o . Calculate the
stored energy before and after introducing a dielectric material.
Solution
The energy stored before introducing the dielectric material,
U =
o
1
2
C V
o
2
o
The energy stored after introducing the dielectric material,
C = κC o
and
V
V ο
d
=
κ
Vo
U
1 2 1
⎛ ⎞ o
U = CV = κCo
⎜ ⎟ =
2
2
⎝ κ ⎠ κ
Therefore, the energy is less by a factor of 1/κ.
2
Dr. Hazem Falah Sakeek