A potentiometer is an instrument for measuring the potential ( or voltage ) in a circuit taps off a fraction of a known voltage from a resistive slide wire and compares it with the unknown voltage by means of a galvanometer .
A potentiometer is an instrument for measuring the potential ( or voltage ) in a circuit . 
 The instrument taps off a fraction of a known voltage from a resistive slide wire and compares it with the unknown voltage by means of a galvanometer .