Question

Why should the emf measured be connected to same side of potentiometer?

Answer 1

A potentiometer is an instrument for measuring voltage by comparison of an unknown voltage with a known reference voltage. If a sensitive indicating instrument is used, very little current is drawn from the source of the unknown voltage. Since the reference voltage can be produced from an accurately calibrated voltage divider, a potentiometer can provide high precision in measurement. The method was described byJohann Christian Poggendorff around 1841 and became a standard laboratory measuring technique.[1]

In this arrangement, a fraction of a known voltage from a resistive slide wire is compared with an unknown voltage by means of a galvanometer. The sliding contact or wiper of the potentiometer is adjusted and the galvanometer briefly connected between the sliding contact and the unknown voltage. The deflection of the galvanometer is observed and the sliding tap adjusted until the galvanometer no longer deflects from zero. At that point the galvanometer draws no current from the unknown source, and the magnitude of voltage can be calculated from the position of the sliding contact.

This null balance measuring method is still important in electrical metrology and standards work and is also used in other areas of electronics.

Answer 2

The potentiometer is a simple device used to measure the electrical potentials(or compare the e.m.f of a cell) One form of potentiometeris a uniform high-resistance wire attached to an insulating support, marked with a linearmeasuring scale.