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Two students X and Y perform an experime...

Two students X and Y perform an experiment on potentiometer separating using the circuit diagram shown here. Keeping other things unchanged
(i) X increases the value of resistance R.
(ii) Y decreases the value of resistance S in the set up. How would these changes affect the position of the null point in each case and why?

Text Solution

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(i) By increasing resistance R, the current in main circuit decreases, so potential gradient decreases. Hence a greater length of wire would be needed for balancing the same potential difference. So, the null point would shift towards right (i.e., towards B).
(ii) By decreasing resistance S, the terminal potential difference `V=E/(1+r/S)`across cell decreases, so balance is obtained at small length i.e., point will be obtained at smaller length. So, the null point would shift towards left (i.e., towards A).
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