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A calibrated potentiometer is used to measure the e.m.f. of a cell because the

A. internal resistance of the cell is small compared with that of the potentiometer

B. potentiometer takes no current from the cell

C. potentiometer has a linear scale

D. resistance of the potentiometer is less than that of a voltmeter

QUICK ANSWER…

B

DETAILS…

A potentiometer is preferred (ahead of voltmeter) when measuring the e.m.f of a cell because it uses the concept of null point to practically draw zero current from the cell.

This is not the case with a voltmeter which can draw some current from the cell. This implies that a potentiometer will give a more accurate measurement than a voltmeter.

Now for the right answer to the above question:

1. Option A is incorrect.
2. Option B is correct. the potentiometer will give a more accurate reading because it takes no current from the cell.
3. C is incorrect.
4. D is not the correct answer. zero resistance.

KEY-POINTS…

You may please note these/this:

• A potentiometer is preferred ahead of a voltmeter in measuring the e.m.f of a cell because it takes no current from it.
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/ culled from 2015 JAMB-UTME physics past question 14 /