Two cells `A` and `B` each of 2 V are connected in series to an external resistance `R=1` ohm.The internal resistance of A is `r_(A)=1.9` ohm and B is `r_(B)=0.9` ohm. Find the potential difference between the terminals of `A`.

Explanation

Total current throught he circuit `i=("voltage")/("total resistance")`
`=(4)/((1+1.9+0.9))=(4)/(3.8)A`
Potential difference at A, `V_(A)=epsi-ir`
`=2-(4)/(3.8)xx1.9=2-2=0`.