A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω and a standard cell of emf 4 V. A constant current flows through…

A potentiometer wire of length $\displaystyle 300$ cm is connected in series with a resistance $\displaystyle 780$ $\displaystyle \Omega$ and a standard cell of emf $\displaystyle 4$ V . A constant current flows through potentiometer wire. The length of the null point for cell of emf $\displaystyle 20$ mV is found to be $\displaystyle 60$ cm . The resistance of the potentiometer wire is \_\_\_\_$\displaystyle \Omega$.