The potential difference in open circuit for a cell is $2.2\, volts$. When a $4\, ohm$ resistor is connected between its two electrodes the potential difference becomes $2\, volts$. The internal resistance of the cell will be .............. $ohm$
A$1$
B$0.2$
C$2.5$
D$0.4$
Medium
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D$0.4$
d $(4 + r)i = 2.2$ ...... $(i)$
and $4i = 2$ $ \Rightarrow $ $i = \frac{1}{2}$
Putting the value of $i$ in $(i)$, we get $r = 0.4\, ohm$.
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