Meter Bridge Calculation — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Meter Bridge Calculation This formula applies when the Wheatstone bridge circuit is balanced, allowing for the accurate determination of an unknown resistance. The Wheatstone bridge circuit is analyzed by applying Kirchhoff's laws. For the bridge to be balanced, the potential difference across the galvanometer must be zero. Setting the galvanometer current to zero leads to the condition that the ratio of adjacent resistances must be equal. This establishes the fundamental relationship: P Q = R S . The bridge must be balanced for the formula to hold. P, Q, R, and S must all be positive resistances. Confusing the ratio of resistances with the actual resistance value. Assuming the formula holds even if the bridge is not balanced (in which case, the galvanometer shows a deflection). Incorrectly assuming that the unknown resistance must be calculated using Ohm's law directly, rather than the ratio method.