# Finding Value of Capcitance and Dissipation Factor of a Given Capacitor by Schering Bridge

Our aim here is to determing the value of the unknown electrical capacitance and dissipation factor of a given capacitor by the Schering’s bridge.

The circuit diagram of the schering’s bridge is as shown in the figure below:

Its connection diagram in the kit is as below:

### Determination of “C” :-

The unknown capacitor C and the unknown resistor R can be found in the equipment. When the bridge is balanced, the following equation is satisfied.

Equating the real and imaginary parts on either sides of the equation we get,

### Determination of Dissipation Factor :-

A practical capacitor can be considered as a pure capacitor in series with a small resistance as shown below:

The phasor diagram is as below:

Dissipation Factor (D.F) = Power factor of capacitor.

### Procedure for Finding Capacitance :-

1. Make connections as shown in the figure. Connect the unknown capacitor using 0.01μFm
2. Set C2 = 0 and R = 0
3. Set R1 = 1000Ω and adjust R2. Adjust both R1 and R2 till you get zero or minimum sound in the headphones.
4. Note down R1, R2, C1 values.
5. Calculate C using the formula C = (C1 R2) / R1
6. Choose different unknown capacitor, repeat the above procedure and find the value of C using equation for C given above.

### Procedure for Finding Dissipation Factor (D.F) :-

1. Without disturbing the setting of the bridge (null points with R1 and R2) introduce R with a initial value say of 500Ω
2. Adjust C2 till you get balance as indicated by minimum or zero sound in the headphones
3. Find D.F using the formula D.F = ω.R.C
4. Repeat above steps with different values of R.

### Other Main Applications of Schering’s Bridge:-

Various other applications of Schering’s bridge include measurements of the properties of insulators, capacitor brushings, insulating oil and other insulating materials.