Unknown Resistance Using Metre Bridge — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Unknown Resistance using Metre Bridge Used in laboratory experiments to find the resistance of a given wire using the Wheatstone Bridge principle. Based on Wheatstone Bridge balance condition: P/Q = R/S. Resistance of segment l (P) is proportional to l. Resistance of segment 100-l (Q) is proportional to 100-l. Ratio P/Q becomes l/(100-l). Equating ratios: l/(100-l) = R/S (if R is on the left gap) or R/l = S/(100-l) depending on placement. Wire must be of uniform cross-section. Contact resistance at the ends (end corrections) must be negligible or accounted for. The jockey should not be rubbed against the wire to avoid changing cross-sectional area. Incorrectly identifying which gap the unknown resistance is placed in. Forgetting that l and 100-l must be measured from the same reference point. Assuming the wire is perfectly uniform when calculating high-precision results.