. The resistivity of a potentiometer wire is \[40\times {{10}^{-8}}\,ohm-m\] and its area of cross-section is \[8\times {{10}^{-6}}\,{{m}^{2}}\]. If 0.2 amp current is flowing through the wire, the potential gradient will be [MP PMT/PET 1998]

• A.                    \[{{10}^{-2}}\,volt/m\]
• B.                                      \[{{10}^{-1}}\,volt/m\]
• C.                    \[3.2\times {{10}^{-2}}\,volt/m\]                            
• D.            \[1\,volt/m\]