| ASSERTION: A potentiometer draws no current while measuring emf of a cell. |
| REASON: Voltmeter is much better than a potentiometer for measuring emf of cell. |
A) If both assertion and reason are true and reason is the correct explanation of assertion.
B) If both assertion and reason are true and reason is not the correct explanation of assertion.
C) If assertion is true but reason is false.
D) If both assertion and reason are false.
E) If assertion is false but reason is true.
Correct Answer: C
Solution :
Potentiometer is preferred for measurement of e.m.f. of cell. Potentiometer draws no current from cell while voltmeter draws some current; therefore, emf measure of voltmeter is slightly less than actual of emf of cell. Further the potentiometer is used with a galvanometer which is set to null reading when the experiment is performed. The method of null reading avoids many errors.
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