Physics - Current Electricity Question with Solution | TestHub

In meter-bridge experiment a resistance of $18\Omega$ is connected in left gap and an unknown resistance $\mathrm{R}$ is connected in right gap. The null point is obtained at ' ${\ell }_1{}^{\circ }$ from left end. If unknown resistance is replaced by $\left(\frac{R}{3}\right)\Omega$, the null point is obtained at $1\cdot 5{\ell }_1$. The unknown resistance is