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Give reason why a potentiometer is preferred over a voltmeter for the measurement of emf of a cell. |
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Answer» Superiority of a potentiometer to a voltmeter : Potentiometer is a null method device. At null point, it does not draw any current from the cell and thus there is no potential drop due to the internal resistance of the cell. It measures the p.d. in an open circuit which is equal to the actual emf of the cell. On the other hand, a voltmeter draws a small current from the cell for its operation. So it measures the terminal p.d. in a closed circuit which is less than the emf of a cell. That is why a potentiometer is preferred over a voltmeter for measuring the emf of a cell. |
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