In order to measure the internal resistance $r_1$ of a cell of emf $\varepsilon$, a meter bridge of wire…
In order to measure the internal resistance $r_1$ of a cell of emf $\varepsilon$, a meter bridge of wire resistance $R_0 = 50 \, \Omega$, a resistance $\frac{R_0}{2}$, another cell of emf $\frac{\varepsilon}{2}$ (internal resistance $r$) and a galvanometer $G$ are used in a circuit, as shown in the figure. If the null point is found at $l = 72 \, cm$, then the value of $r_1 = \_\_\_\_ \, \Omega$.
