A potentiometer wire has a uniform potential gradient. The specific resistance of the material of the wire is \( 10^{-7} \) ohm-m, the current passing through it is 0.1 A and its cross-sectional area is \( 10^{-6}\,\mathrm{m^{2}} \). What is the value of the potential gradient?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 10^{-2}\,\mathrm{V\,m^{-1}} \)
The potential gradient of a potentiometer wire is the potential drop per unit length. Using Ohm’s law and \( R = \rho l/A \), the length cancels:
\( \displaystyle k = \frac{V}{l} = \frac{IR}{l} = \frac{I\rho}{A} \)
\( \displaystyle k = \frac{0.1\times10^{-7}}{10^{-6}} = 10^{-2}\,\mathrm{V\,m^{-1}} \)