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

`R= 10 Omega,`
Balancing length `l_1 = 560 cm`
Change in balancing length `(l_1 - l_2) = 60 cm`
internal resistance = r= ?
`l_1 - l_2 = 60 , 56 - l_2 = 60`
`therefore l_2 = 500 cm`
`r= R((l_1 - l_2)/(l_2)) = 10 xx (60)/(500) = 6/5 = 1.2 Omega`