$10\, Cells$, each of $emf$ $'E'$ and internal resistance $'r'$, are connected in series to a variable external resistance. Figure shows the variation of terminal potential difference of their combination with the current drawn from the combination.$Emf$ of each cell is ................ $V$
A$1.6$
B$3.6$
C$1.4$
D$4.2$
Medium
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D$4.2$
d $6=10 \mathrm{\,E}-12(10 \mathrm{\,r})$ ..........$(1)$
So, $6=10 \mathrm{\,E}-12\left[10 \times \frac{\mathrm{E}}{14}\right]$
$E=\frac{42}{10}=4.2 \mathrm{\,V}$
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