Figure Of Merit Of A Galvanometer — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Figure of Merit of a Galvanometer This formula is used in experimental physics to determine the sensitivity and figure of merit of a moving coil galvanometer using a standard cell and a resistance box. Apply Ohm's Law to the series circuit containing the battery, resistance box, and galvanometer: I = E / (R + G). Recall the principle of the moving coil galvanometer where Current (I) is proportional to Deflection ( ): I = k . Equate the current expressions: k = E / (R + G). Rearrange to solve for the Figure of Merit k: k = E / ((R + G) ). The deflection should remain within the scale (usually 0-30 or 0-50). R must be sufficiently large to limit current within the safe range of the galvanometer. Applicable only to DC circuits with linear deflection response. Confusing Figure of Merit (k) with Current Sensitivity (S i). Note that S i = 1/k. Ignoring the Galvanometer resistance (G) in the denominator when R is not significantly larger than G. Thinking 'div' (division) is a standard SI unit; it is a dimensionless count on the scale.