Two students ‘X’ and ‘Y’ perform an experiment on potentiomete

1.	Two students ‘X’ and ‘Y’ perform an experiment on potentiometer separately using the circuit given.Keeping other parameters unchanged, how will the position of the null point be affected if(i) ‘X’ increases the value of resistance R in the set-up by keeping the key K1 closed and the key K2 open?(ii) ‘Y’ decreases the value of resistance S in the set-up, while the key K2 remain open and the key K1 closed? Justify your answer in each case.
Answer» (i) By increasing resistance R the current through AB 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 B. (ii) By decreasing resistance S, the current through AB remains the same, potential gradient does not change. As K₂ is open so there is no effect of S on null point.

Two students ‘X’ and ‘Y’ perform an experiment on potentiometer separately using the circuit given.Keeping other parameters unchanged, how will the position of the null point be affected if(i) ‘X’ increases the value of resistance R in the set-up by keeping the key K1 closed and the key K2 open?(ii) ‘Y’ decreases the value of resistance S in the set-up, while the key K2 remain open and the key K1 closed? Justify your answer in each case.

Answer»

(i) By increasing resistance R the current through AB 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 B.

(ii) By decreasing resistance S, the current through AB remains the same, potential gradient does not change. As K₂ is open so there is no effect of S on null point.

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