Question

In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should
(a) decrease resistance in the main circuit.
(b) increase resistance in the main circuit.
(c) decrease resistance in series with the cell whose emf is to be measured.
(d) increase resistance in series with the cell whose emf is to be determined.

Answer 1

Answer:

THE ANS TO THIS IS B i.e. INCREASE RESISTANCE IN THE MAIN CIRCUIT BECAUSE WHEN YOU INCREASE RESISTANCE CURRENT IN THE WIRE DECREASES DUE TO WHICH POTENTIAL GRADIENT (V/l) DECREASES  AND NULL POINT LENGTH IS INVERSELY PROPORTIONAL TO POTENTIAL GRADIENT SO IT WILL INCREASE FROM 7 TO 9.

V=IR                  [I=current and R=resistance]

=> V/L=I rho/A => V/L(K) is proportional to I

and we know I=V/R  so I is inversely proportional to R

HOPE IT HELPS YOU

Explanation: