why only potentiometer is used to measure emf of cell and not voltmeter?

by using the voltmeter it takes current through itself(device) (its resistance is very high) and thus causes some wrong measurement in finding the potntial diff. as current is used the internal resistance also causes some use of voltage. thus by using it it gives a wrong reading. generally less than emf o cell.

bt with potentiometer the arrangemrnt is such that by comparing n moving jockey a ome point the bttey (whose emfis to be calculted) draws no current and thus gives correct emf or reading. potentiometeris basiclly a arrangement .

please try to understand the concept of potentiometer and logic by reading in book or with a teacher.

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