Meter bridge

Aim

Balance a meter bridge and use its wire lengths to find an unknown resistance.

1. Describe what zero galvanometer current means at balance.
2. Calculate an unknown resistance from the wire-length ratio.
3. Explain the advantage of finding balance near the middle of the wire.

Apparatus

1. Meter-bridge board with a uniform resistance wire
2. Resistance box for known R and a resistor with unknown X
3. Low-voltage supply, galvanometer, jockey contact, and switch