If specific resistance of a potentiometer wire is $10^{-7} \Omega m$ and current flow through it is 0.1 A, cross-sectional area of wire is $10^{-6} m^2$ then potential gradient will be :-

Question

( A ) $10^{-8} V/m$
( B ) $10^{-6} V/m$
( C ) $10^{-4} V/m$
( D ) $10^{-2} V/m$