Meter bridge

Procedure

1. Turn the supply off. Fit the unknown X in the left gap and known R in the right gap.
2. Connect the supply to the wire ends. Connect the galvanometer between the central junction and the jockey.
3. Close the switch briefly. Touch the jockey gently at separate positions to find where the deflection changes direction.
4. Locate the zero-deflection point. Measure l from the left end and use the ratio to calculate X.
5. Try different R values so that balance lies near 50 cm. Swap X and R, record their new positions, and check your result.

Precautions

1. Lift and place the jockey gently; dragging it can damage the wire. Allow current only briefly.
2. Write down which gap holds X before choosing the length ratio.