The potentiometer wire AB shown in figure is 40 cm long. Where should the free end of the galvanometer be connected on AB so that the galvanometer may show zero deflection?

Explanation

If the wire is connected to the
potentiometer wire so that
` R_AD/R_DB = 8/12 `
then according to Whitstone's bridge, no
currrent will flow through galvano meter.
` R_AD/R_DB = L_AD/L_DB = 8/12 = 2/3 `
(Acc.to principle of potentio meter)
` L_DB+L_DB = 40 cm `
` rArr L_B 2/3 + L_DB = 40 cm `
` rArr 5/3 L_DB = 40 cm `
` rArr L_DB = 40 xx 5/3 `
= 24 cm from B.