Physics - Current Electricity Question with Solution | TestHub

A wire AB (of length 1 m , area of cross section $\pi {\mathrm{m}}^2$ ) is used in potentiometer experiment to calculate emf and internal resistance ( r ) of battery. The emf and internal resistance of driving battery are 15 V and $3\Omega$ respectively. The resistivity of wire AB varies as $\rho ={\rho }_0\mathrm{x}$, where x is distance from A in meters and ${\rho }_0=24\pi \Omega$. The distance of null point from $A$ is obtained at $\sqrt{\frac{2}{3}}m$ when switch ' $S$ ' is open. Find the value of $E$.