Answer:
[tex]r = 0.043 ohm[/tex]
Explanation:
As we know that total potential of all cells when they are in series is given as
[tex]V = V_1 + V_2 + V_3 + ....................[/tex]
so we have
[tex]V_{net} = 12(2.1) = 25.2 Volts[/tex]
now total resistance of all 12 cells which are in series is given as
[tex]r_{net} = 12 r[/tex]
external resistance is given as
[tex]R = 2 ohm[/tex]
now by Ohm's law we know that
[tex]V_{net} = i (R + r_{net})[/tex]
so we have
[tex]25.2 = 10 (2 + 12 r)[/tex]
[tex]r = 0.043 ohm[/tex]
