Measurement of the unknown capacitance schering bridge method.

Aim:- Measurement of the unknown capacitance schering bridge method.

Apparatus:- Sharing bridge kit

digital multimeter,

patch cords,

Circuit Diagram:-

Theory:-

The schering bridge one of the most important ac bridge is used the extensively for the

measurement of capacitors.

In the schering bridge the arm 1 now contains a parallel combination of the

resistor and the capacitor and standard arm contain only one capacitor. The standard

capacitor is usually a standard high quality mica capacitor.

in the balance condition of the bridge the sum of the phase angles of the arms 1

and 4 is equal the sum of the phase angle of arms 2 and 3.at the balance in condition there

is no current flow in the galvanometer.

The balance equation is derived in the usual manner, and by substituting the

corresponding impendence and the admittance the value of the unknown capacitor and

the resister is find as given below.

Cx=C3(R1/R2).

Rx=R2(C1/C2)

Procedure: -

1) Study the circuit provided on the front panel on the kit.

2) Connect the unknown capacitance of the position given.

3) Set the null point of galvanometer by adjusting the variable

4) Calculate the value of unknown capacitance by formula given

Result: -The values of unknown capacitance is measured by shearing bridge

Viva Questions-

1)What is the Q factor of the coil?

2) Which bridges are used for measurement of inductance

3) What is the range of Q?

Experiment no-8

Aim-. Measurement of the 3phase power by the one watt meter method.

Apparatus:-

Three phase variable load.

Wattmeter (0-5A)-, 300v-1no

Ammeter (0-10A)-1no

Voltmeter (0-600v) , (0-300v)-1no

Three phase variance.

Circuit Diagram:-

Theory:-

In this method the total power is consumed is calculated by using the one wattmeter .

This method is used only if the load is balanced The ammeter is connected in between the

coil to the same size and line. The other terminal is connected by the two lines. In this

method the wattmeter is first connected with the R phase and then the B phase The rating

of these two conditions are summed by the total power consumed

Here-V1=V2=V3=V

& I1=I2=I3=Iline

&V13-V12=V23=Ö3V

Reading of wattmeter when connected to phase R

P1=V12*Il*(30-A)

P1=VIÖ3cos(30-A)

Reading of wattmeter when connected to phase B

P2=V12IL(30+A)

P2=Ö3Vicos(30+A)

Sum of two conditions

P=P1+P2

P=Ö3Vi{cos(30-A+cos(30+A)}

P=3VicosA

This equation gives total power consumed by load.

Observation Table:-

Sr no Voltage Current Power 3 phase watt

Procedure:-

1) Make the arrangement as per the circuit diagram.

2) Increase the dimmerstat reading

3) Note the corresponding values of voltmeter ,ammeter and wattmeter.

4) Take consequent 3 readings.

Result:- Hence in that way calculated the 3phase Power by one watt meter method.

Viva Questions:-

1) Explain the short how the wattmeter is connected in the circuit to .

Measure the power delivered to the Load and the Line.

2) Explain How the Resistive Power is measured by the Wattmeter

Method