In a balanced Wheatstone bridge circuit, four resistors P, Q, R, and S form the four arms, and a galvanometer is connected across the bridge. What is the mathematical condition for zero deflection in the galvanometer?

💡 Solution & Explanation

A Wheatstone bridge is balanced when no current flows through the galvanometer, which occurs precisely when the ratio of resistances in adjacent arms is equal, expressed as P over Q equals R over S. This principle is used for accurate measurement of unknown resistances by comparing them with known standard resistors. Kirchhoff rules of circuit analysis are used to derive this balance condition. Electrical resistivity depends on the material temperature and composition.