Question

In the circuit shown, the variable resistance is so adjusted that the ammeter reading is same in both the position $1$ and $2$ of the key the reading of ammeter is $2\text{A}$. If $E=10\text{V}$ and internal resistance$=0,$ then find $x.$ (in ohm)

Answer 1

Given
$I=2\text{A}$
$E=10$ volt
$r=0$
Let unknown emf of cell is and reheostar resistance is $r$
At position $1$
$ϵ-Ir=0$
$ϵ=2r$
At position $2$
$ϵ-ir+E-ix=0$
$10=2x$
$\Rightarrow x=5\Omega$