For the circuit would the balancing length increase, decrease or remain the same if (i) `R_(1)` is decreased (ii) `R_(2)` is increased, without any change (in each case) in the rest of the circuit ? Justify your answer in each case.

Explanation

(a) (i) When `R_(1)` is decreased, the balancing length AJ will decrease, we will have to move the Jockey J towards A.
as by decreasing `R__(1)` potential gradiant across wire AB will increase `l=(V)/(K)`
hence 1 (AJ) will decrease.
(ii) When `R_(2)` is increased. Potential drop across `R_(2)` will increas. Hence the blanacing length AJ will increase. We will have to move the Jockey J towards B.
(b) A potentiometer being a null device, does not draw any current from the balance point therefore potentiometer measures the actual e.m.f. of the cell. Whereas, voltmeter always draw current from the cell and measures the terminal voltage of the cell instead of the actual emf of the cell.