• summary_type: application
• word_count: 160

The metre bridge implements a Wheatstone bridge using a uniform resistance wire. Balance condition: R/X = l/(100-l), giving X = R(100-l)/l. The galvanometer shows zero deflection at the null point. For best sensitivity, choose R so that the null point is near l = 50 cm (when X ≈ R). This minimizes percentage error: Delta_X/X = Delta_R/R + Delta_l*(1/l + 1/(100-l)). At l = 50: the error term is 2*Delta_l/50 = Delta_l/25, which is minimized. End corrections (alpha, beta) account for resistance of copper strips: corrected formula R/X = (l+alpha)/(100-l+beta). To find end corrections, use two known resistances. Interchanging R and X (swapping gaps) and averaging results cancels some systematic errors. JEE problems: find X, determine the sensitivity at a given null point, or analyze how errors propagate.