Meter Bridge is used to determine unknown resistance Rc.

- The meter bridge is a device used to measure the unknown resistance of a conductor. It is based on the principle of Wheatstone bridge, which is a circuit arrangement used to measure resistance accurately.
- The meter bridge consists of a uniform wire AB of length L, which is mounted on a wooden base. A galvanometer G, a battery B, a jockey J, and a resistance box are connected in the circuit.
- The unknown resistance Rc is connected in series with the resistance box, and the jockey is used to slide along the length of the wire and make contact with it.
- The principle of operation of the meter bridge is based on the balancing of the bridge circuit. When the jockey is moved along the wire, a point is reached where the galvanometer shows no deflection, indicating a balanced condition.
- At this point, the ratio of the resistances on either side of the jockey is equal. This can be expressed as: Rc / R1 = R2 / R3, where R1 is the resistance in the resistance box and R2 and R3 are the known resistances on either side of the jockey.
- By measuring the known resistances and the length of wire on either side of the jockey, the unknown resistance Rc can be calculated using the above equation.
- The meter bridge is a very accurate method for measuring resistance as it eliminates errors due to contact resistance and internal resistance of the wire.
- The accuracy of the measurement can be improved by using a long wire and taking multiple readings at different positions of the jockey.
- The meter bridge can be used to measure the resistance of various conductors such as wires, resistors, and coils, as long as they can be connected in the circuit and have a measurable resistance.