DCC WIRE A galvanometer is converted into a voltmeter by connecting a high resistance (multiplier) in series with the galvanometer coil.
Principle
Role of a Voltmeter: A voltmeter measures the potential difference (voltage) between two points in a circuit and must be connected in parallel across that component.
Preventing Circuit Disturbance: An ideal voltmeter has infinite resistance so it draws negligible current from the main circuit and does not alter the voltage it measures.
Limiting Galvanometer Current: A standard galvanometer has a low internal resistance (G) and gives full-scale deflection at a very small current (Ig). To let it measure a large voltage (V) without burning out the coil or drawing too much current, a large series resistance (R) is added to drop most of the voltage.
