A resistance of $4\,\Omega $ and a wire of length $5\,m$ and resistance $5\,\Omega $ are joined in series and connected to a cell of $e.m.f.$ $10\, V$ and internal resistance $1\,\Omega $. A parallel combination of two identical cells is balanced across $300\, cm$ of the wire. The $e.m.f.$ $E$ of each cell is ........... $V$
A$1.5$
B$3$
C$0.67$
D$1.33$
Medium
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B$3$
b $E = x\,l = \frac{V}{l} = \frac{{iR}}{L} \times l$
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