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Physics · 2025 · 2 marks
CBSE 2025 · Region 1 · Set 3 · Q17
n identical cells, each of e. m. f. E and internal resistance r, are connected in series. Later on it was found out that two cells' X 'and' Y 'are…
n identical cells, each of e. m. f. E and internal resistance r, are connected in series. Later on it was found out that two cells' X 'and' Y 'are connected in reverse polarities. Calculate the potential difference across the cell' X '.
Marking-scheme solution
Net e.m.f. $\displaystyle =(n-4) E$
$\displaystyle \therefore I=\frac{(n-4) E}{n r}$
Potential difference across X:
$\displaystyle V=E+I r$
$\displaystyle =E+\frac{(n-4) E \times r}{n r}$
$\displaystyle =\frac{(2 n-4) E}{n}$
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