الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Capacitors and capacitance
6.6 Capacitor with dielectric
A dielectric is a non-conducting material, such as rubber, glass or paper.
Experimentally it was found that the capacitance of a capacitor increased
when a dielectric material was inserted in the space between the plates. The
ratio of the capacitance with the dielectric to that without it called the
dielectric constant κ of the material.
C
κ = (6.18)
C
ο
In figure 6.14 below two similar capacitors, one of them is filled with
dielectric material, and both are connected in parallel to a battery of
potential V. It was found that the charge on the capacitor with dielectric is
larger than the on the air filled capacitor, therefore the C d >C o , since the
potential V is the same on both capacitors.
C o
V
C d
K
Figure 6.14
If the experiment repeated in different way by placing the same charge Q o
on both capacitors as shown in figure 6.15. Experimentally it was shown
that V d <V o by a factor of 1/κ.
C o
V o
C d
K
V d
Figure 6.15
V
V ο
d
= (6.19)
κ
Since the charge Q o on the capacitors does not change, then
www.hazemsakeek.com