1) Dielectric materials have a dielectric constant (ε) which describes their ability to be polarized by an external electric field. Materials with higher dielectric constants store more electrical energy. 2) The dielectric constant of water is 78.5, much higher than most other materials like glycerol at 42.5 or ethanol at 24.3. This is why water is commonly used as a dielectric in capacitors. 3) The dielectric constant determines the capacitance of a capacitor. Capacitance increases as the dielectric constant increases for a given capacitor geometry.

1. 1
(Dielectric)
k
---
dielectric constant, ε) )
electrical properties)
polarity)
dielectric
material) polar)
-
C =
kC
0

2. 2
dielectric material) 78.5
-
3.2
NaCl)
electrolyte
Dielectric constant

3. 3
Dielectric constant
Non polar 1-20
semipolar 20-50
polar >50
-
- frozen food)

4. 4
25
Dielectric constant
Water 78.5
Sorbitol solution (70%w/w) 62.0
Syrup USP 56.0
Glycerol 42.5
Methanol 32.6
Propylene glycol 32.1
Ethanol 24.3
acetone 20.7
Isopropyl alcohol 18.3
Benzyl alcohol 13.1
Polyethylene glycol 400 12.4

5. 5
capacitance)
(

6. 6

7. 7

8. 8
= j
= complex relative
permittivity
= real
= imaginary

9. 9
permittivity in free space,
= 8.854 × 10¯¹² F m
=
= = j
1
loss factor
loss tangent, tan
vector analysis
90
°

10. 10
tan = =
= =
8.854 × 10¯¹²
F m
C F
t m
A m²
Dissipation factor, D

11. 11
Capacitor) Charge)
Discharge) 2
Dielectric) , , ,
3.1
3.1
1 2
3

12. 12
Charge)
Discharge)
Coulomb)
Farad)
3.2
3
A

13. 13
d

14. 14
Fixed
Capacitor)
5 PF) 10
uF)
,
,

15. 15
(a) (b)
- (Nonconducting
Material)

16. 16
-
k
(DielectricConstant )
V0 = Q0 / C0
k V0
V< V0 k> 1
Q0
C0
k
V
V 0
0
0
0
00
V
Q
k
k/V
Q
V
Q
C kCC 0

17. 17
C0= 0A/d
d
d
d
(Dielectric
Strength)
d
A
kC 0

18. 18
. . 1837
1.42
V0
V
C0
C
V V0 C C0

19. 19
k
(dielectric constant)k = C / C0 1
20
1 2.1
5 -10 16
3 – 6 80.4
3.1 42.5
Neoprene
6.7 2.284
2.25
-78 C
25
3.18 1 1.0059

20. 20
(dipole)
(dielectric
breakdown)

21. 21
.
.
.
/
2 i / 2
E
E = E - Eᵢ= Vd = –
k = C C = V V = E E =
= =

22. 22
E =
permittivity
C = kC = =
k =
k = 1
k
.
- (dipole)

23. 23
-
-
polarization)
-
-

24. 24
- (nonpolar
molecule)
-
- 0E

25. 25
-
-
ind
ind
indE
0E

26. 26
-
-
-
-
--

27. 27
http://www.doitpoms.ac.uk/tlplib/dielectrics/dielectric_consta
nt.phphttps://www.google.co.th/#fp=afad fdd ea b&q
http://www.foodnetworksolution.com
http://www.rit.ac.th/homepage-sc/physics/
http://kpp.ac.th/elearning/elearning3/book-03.html