Question: In the potentiometer arrangement shown, the driving cell D has e.m.f. E and internal resistance r. T...

Question

In the potentiometer arrangement shown, the driving cell D has e.m.f. E and internal resistance r. The cell C whose e.m.f. is to be measured has e.m.f. E/2 and internal resistance 2r. The potentiometer wire is 100 cm long. If the balance is obtained the length AP = l, then-

Answer 1

Solution

V_A – V_B < E

V_A – V_P = E/2

$\frac { V _ { A } - V _ { B } } { V _ { A } - V _ { P } }$ = $\frac { \ell _ { 0 } } { \ell }$

V_A – V_B = $\frac { \ell _ { 0 } } { \ell }$ < E

l > $\frac { \ell _ { 0 } } { 2 }$ Þ l > 50 cm