Suppose two cells of emf and internal resistance e1, r1 and e2, r2 respectively are connected in series. The negative electrode of 1st cell is connected to negative electrode of the second cell. Why is the voltage drop across the second cell (-e2-Ir2) (I is the current) but not (-e2+Ir2)?
In my intuitive sense of speaking, for example, if there was just one cell with current I being drawn from it, then the terminal voltage is (e - Ir) as the current emerges from the positive electrode and the voltage drop across internal resistance is negative as internally the cell current emerges from negative electrode.
The negative e2 in the series combination makes sense as the current emerges from the negative electrode of the cell, but why is the potential drop across internal resistance still negative as even though the cell's internal current emerges from the positive electrode this time?
The only time I know this makes sense is when it is charging, but even with charging of cell the problem shifts to the sign of emf instead. I think I'm going wrong somewhere with this interpretation, and if so, is there a better way to interpret this intuitively? Attached photo is for reference of the setup I'm concerned for