A battery of unknown emf connected to a potentiometer has balancing length 560 cm. If a resistor of resistance 10 ohm, is connected in parallel with the cell the balancing length change by 60 cm. If the internal resistance of the cell is `n/10` ohm, the value of 'n' is

Explanation

Balancing length `l_(1)=560 cm`
Change in balancing length `(l_(1)-l_(2))=60cm`
`560 -l_(2)=60" "therefore l_(2)=500cm`
`r=R((l_(1)-l_(2))/(l_(2)))rArr r=10xx(60)/(500)=(6)/(5)=1.2Omega`