Objective: To determine the relative permittivity of an unknown capacitor.

Fig. 1. Relative Permittivity measurement by Schering Bridge circuit.

The circuit diagram is shown in Fig.1.

Let, C_{1}=capacitor whose capacitance is to be measured.

r_{1}= a series resistance representing the loss in the capacitor C1.

C_{2}= a standard capacitor.

R_{3}= a non-inductive resistance.

C_{4}= a variable capacitor.

R_{4}= a variable non-inductive resistance.

d= Spacing between electrodes,

A= effective area of electrodes,

= permittivity of free space.

At balance,

Equating the real and imaginary terms in equ. (2), we obtain

and,

Two independent balance equations (3) and (4) are obtained if C_{4} and R_{4} are chosen as the variable elements.

Dissipation factor ,

For, a parallel plate arrangement , relative permittivity,