To determine the dielectric constant of different materials by resonance method
AIM: To determine the dielectric constant of different materials by resonance method
APPARATUS REQUIRED: RF Oscillator, Test Capacitor, Variable Capacitor, Test Dielectric
Material and Patch Cords
FORMULA: The dielectric constant is given by:
K =
𝐶.𝑑
𝜀0𝐴
Where, d = distance between two plates
A = Area of plate
C = Capacitance
ε0 = free space permittivity 8.854 X 10-12 Fm-1
Instructions:
1. Test capacitor's plate must be tight when filled with dielectric material.
2. Observations must be taken carefully.
3. Patch cords should be tightly connected.
Observations:
Dielectric
Sample
Gap
between
plates (d) in
(m)
C1
(without
sample)
(pF)
C2 or C3
(with
sample)
(pF)
C1 - C2 or
C3 - C2
(pF)
Teflon
(known)
K1 = 2.35
d1 = 3.1×10-3 248 C2 = 223 C1 - C2 = 25
𝜖0𝐴 =
(c1 − c2)d1
K1
=32.9x10-3
Bakelite
(unknown)
K2 = ?
d2 = 6.5×10-3 248
C2 = 215 C1 – C2 = 33
𝐾2 =
(c1 − c2)d2
ϵ0A
=6.51
C3 = 234 C3 - C2 = 19
𝐾2 = 1 +
(c3 − c2)d2
ϵ0A
=4.75
Result: The dielectric constant of material = 4.75