Physics - Current Electricity Question with Solution | TestHub

A potentiometer can also be used to calibrate an ammeter or a voltmeter. Here, we require a standard cell whose electromotive force (EMF) is known, say $E$. This cell is connected to the secondary branch of the potentiometer, and we balance this standard cell against a length $l$ on the potentiometer wire (by connecting points 1 and 2). Now, the standard cell is removed, and the galvanometer end 2 is connected to point 3 on the circuit and balanced against length $l$. Current $I$ can be obtained using the principle of the potentiometer as well as from the ammeter. The current $I$ as given by the potentiometer is the true value, and the ammeter reading may have an error.