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.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is true

Answer

A

Explanation

Potentiometer is used to measure the e.m.f. of a cell. The assertion is true.
Voltmeter draws certain amount of current from the cell. So, V = E - iR. The measured value by the voltmeter is less than the actual e.m.f. of the cell. But potentiometer draws no net current at balance point, hence it measures the actual e.m.f. of the cell. So, the reason is also true and explains the assertion properly.