Write principle of potentiometer. Why potentiometer is preferred over voltmeter for measurement of emf of cell. For the potentiometer circuit shown in figure, point X andY represent the two terminals of an emf E. . , A student observed that when the jockey is moved from the end A to the end B of the potentiometer wire, the deflection in the galvanometer remain in the same direction. What may be the two possible faults in the circuit that could result in this observation? If the galvanometer deflection at the end B is (i) more, (ii) less , than that at the end A, which of the two faults, listed above, would be there ln the circuit? Give reasons in support of your answer in each case.
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A voltmeter should not be used to measure the emf of a cell as a voltmeter draws some current from the cell during measurement. When voltmeter is connected across the cell it amounts to closed circuit measurements and there is inner potential drop due to internal resistance of the cell. Therefore, the measurement of cell's emf will not be accurate
To measure a cell's emf, use of a potentiometer is preferred since in potentiometer-measurement no current flows through the cell. It is an open circuit measurements. The emf of cell will be measured accurately.
Other advantages of using a potentiometer are
Sensitivity of potentiometer is high as compared to that of voltmeter.The resistance of potentiometer becomes infinite at the time of measurement. Whereas in case of voltmeter the resistance is very high but still a measurable number.Similar questions