The potentiometer is an instrument used for the measurement of potential difference. It consist of a ten meter long uniform wire of manganin or constantan stretched in ten segments, each of one meter 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 meter scale is fixed on the board, parallel to the wire. Electrical contact with wires is established by pressing the jockey.