Question

Assertion A potentiometer is preferred over that of a voltmeter for measurement of emf of a cell. Reason Potentiometer does not draw any current from the cell.

• A. Both assertion and reason are true and reason is the correct explanation of assertion
• B. Both assertion and reason are true but reason is not the correct explanation of assertion
• C. Assertion is true but reason is false.
• D. Both assertion and reason are false.

Answer 1

Answer: (A)

When a voltmeter is connected across the two terminals of a cell, it draws a small current from the cell, so it measures terminal potential difference between the two terminals of the cell, which is always less than the emf of the cell on the other hand, when a potentiometer is used for the measurement of emf of cell, it does not draw any current from the cell. Hence, it accurately measures the emf of cell. Thus, a potentiometer is preferred over a voltmeter.