To study the Kelvin Double Bridge for Low resistance measurement            

Procedure

Figure 1: The circuit diagram for experimental set-up of Kelvin Double Bridge

1. Connect the circuit as shown in the Fig. 1.

2. Set the value of the resistances A and a at 1000 ohm by setting the plugs at the marked positions and the values of B, b at 1000 ohm by setting the dial. Open the Key K. The bridge will act as a wheatstone bridge. A null deflection Galvanometer will ensure the relationship A/a = B/b.

3. Close the key K. Adjust the rheostat to obtain 2A current in the circuit .

4. Keeping the resistances A, a at 1000 ohm, vary B, b to obtain the Galvanometer null. Note the value B, b at balance position from the dial.

5. Reverse the direction of current by operating the two-way switch 's' and obtain the balance.

6. Set the values of A, a at 1 ohm and 1000 ohm position and repeat step 5 and step 4.

7. Repeat step 5 through step 6 for different line currents 3A, 4A and 5A.