State Principle and Construction of a Meter Bridge with neat diagram

Meter Bridge:

A meter bridge is shown below figure. AC is a thin conducting wire of uniform cross-sectional area and length of 1m which is clamped between two thick copper strips. A meter scale is fixed on the base along the wire. A variable known resistance box R is connected across the left gap and the unknown resistance S to be measured is connected across the right gap of the meter bridge.

A galvanometer G is connected between D and the jockey J which can be slid along the wire. With the help of the jockey electrical contact can be made at any point of the wire.