The `EMF` of a galvanic cell is measured by

Options

A. ammeter
B. galvanometer
C. voltmeter
D. potentiometer

Answer

D

Explanation

The capacity to do electical work by a cell is called lthe cell potential. It is expressed in volt `(V)`. We could use a voltmeter to measure the cell potenital but this would not give us the correct value of cell potential. The reason is that the cell potenital is dependent upon the concentreation of the elctrolyte which would change if we allow the current to flow in the circuit through the voltmeter. Hence, we must measuure the potential difference betweent he two half-cells when the cell is hald at almost constant composition and no current is flowing
The potential differnce of a cell when no current is drawn out and when the cell is operating reversibly (i.e., very-2 slowly) is called the `emf` (electromotive force) of the cell. The measurement of the `emf` can by done by using a pote-tiometer. The potentioeter consits of a wire of uniform cross-section and high resistance so that negligible current is drawn out during the measurement. We make use of Weston cadmium cell (a commonly used standard cell) for the standardization) of a potentiometer.