In the given figure, battery $E $ is balanced on $55\, cm$ length of potentiometer wire but when a resistance of $10 \,\Omega$ is connected in parallel with the battery then it balances on $50\, cm$ length of the potentiometer wire then internal resistance $r$ of the battery is ............. $\Omega $
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In an experiment to find $emf$ of a cell using potentiometer, the length of null point for a cell of emf $1.5\,V$ is found to be $60\,cm$. If this cell is replaced by another cell of $emf\; E$. the length-of null point increases by $40\,cm$. The value of $E$ is $\frac{x}{10} V$. The value of $x$ is $............$
Two rods of copper and iron with the same cross-sectional area are joined at $S$ and a steady current $I$ flows through the rods as shown in the figure. Choose the most appropriate representation of charges accumulated near the junction $S$.