Dielectric Constant 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/Eo A


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 a dielectric material.
2. Observations must be taken carefully.
3. Patch cords should be tightly connected.

Principle:

In the high-frequency range resonance methods are generally used to measure the capacitance and the dielectric constant. Resonance method involves the injection of voltage or current into an L-C resonant circuit. An oscillatory circuit that includes a standard capacitor is tuned to resonance and the corresponding value of capacitance  is determined.  Then a capacitor with the dielectric ( ) is connected in parallel with the standard capacitor and the circuit is again tuned to resonance.  In the second case, the capacitance  of the standard capacitor will be smaller.  

Observations:

Result: The dielectric constant of material = 4.75