Two cells of emfs approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm.? Mark as favorite Copy Link Potentiometer is usually used for comparing resistances and not voltages. The battery that runs the potentiometer should have voltage of 8V. The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V. The first portion of 50 cm of wire itself should have a potential drop of 10 V Check Answer