The area of cross-section of a potentiometer wire is $6 \times 10^{-7}$ m$^2$. The potential difference per unit length of the potentiometer wire when it is connected to a cell of negligible internal resistance and a resistor in series is $0.15$ Vm$^{-1}$. If the current through potentiometer wire is $0.3$A, then the resistivity of the material of the potentiometer wire is
Show Hint
The potential gradient ($k$) in a potentiometer is directly proportional to the current ($I$) and the resistivity ($\rho$), and inversely proportional to the cross-sectional area ($A$) of the wire ($k = I\rho/A$). This relationship is a consequence of Ohm's law and the definition of resistivity.
