A Wheatstone bridge is an electrical circuit used to measure an unknown resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The circuit consists of four resistors, with a voltage source connected to two opposite corners and a galvanometer connected to the other two corners.

By adjusting the values of the resistors in the bridge, the circuit can be balanced and the value of the unknown resistor can be calculated. Wheatstone bridges are commonly used in scientific and engineering applications to measure small changes in resistance or to accurately determine the value of an unknown resistor. They are also used in strain gauge measurements, where changes in resistance due to mechanical strain can be measured with high accuracy.