Potentiometer — A/L Physics

Potentiometer A device used to measure potential difference (voltage) without drawing any current from the source. Unlike a voltmeter, which has finite resistance and draws some current, a potentiometer compares voltages under null condition (zero current flow), giving true EMF readings. It consists of a long uniform resistance wire (typically 1–10 m) connected across a driver cell.

Principle of Potentiometer The potential difference across any length of a uniform wire is directly proportional to that length when a constant current flows through it. If a wire of uniform cross-sectional area and resistivity carries a steady current, the potential drop per unit length (potential gradient, k ) is constant. Thus, V ∝ l . This linear relationship allows voltage comparison by measuring lengths along the wire.