The Potentiometer is an instrument used for the measurement of potential difference (Figure). It consists of a ten metre long uniform wire of manganin or constantan stretched in ten segments, each of one metre length.
The segments are stretched parallel to each other on a horizontal wooden board. The ends of the wire are fixed to copper strips with binding screws. A metre scale is fixed on the board, parallel to the wire. Electrical contact with wires is established by pressing the jockey J.