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