A modified potentiometer for measuring very small resistances

Abstract

Two changes in the circuit arrangement of a potentiometer as used for resistance measurements were found to reduce considerably troubles due to "residual E.M.F." The changes were: (1) breaking both battery circuits, instead of the galvanometer circuit, to test for balance; (2) making reduction of the battery potential by a fixed potential divider follow, instead of precede, that by the potentiometer box itself. Some points of practical significance are discussed.