Wheatstone Bridge A Wheatsone Bridge is a useful circuit arrangement that allows accurate measurement of resistance.

A Wheatstone bridge is "balanced" by adjusting resistors R

_{3}and R_{4}so that no current flows through the Galvanometer. Then, the voltage at points A and B in the circuit is the same. Voltage across R_{1}is the same as across R_{3}and the voltage across R_{x}is the same as across R_{4}. Current through R_{1}and R_{x}is the same and current through R_{3}and R_{4}is the same.Since points A and B have a common potential we can write

I _{1}R_{1}= I_{3}R_{3}Likewise, we can write

I _{1}R_{x}= I_{3}R_{4}Dividing one equation by the other, we have

We can replace the variable resistors R

_{3}and R_{4}with aslidewirewith variable length L_{3}and L_{4},

Return to Ch 19, DC Circuits(c) Doug Davis, 2002; all rights reserved