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A wire $50\, cm$  long and $1\;mm^2$ in cross -section carries a current of $4\; A$ when connected to a $2\; V$ battery. The resistivity of the wire is
  • A$1 \times  {10^{ - 6}}\;\Omega-m$
  • B$4 \times  {10^{ - 6}}\;\Omega-m$
  • C$5\times  {10^{ - 7}}\;\Omega-m$
  • D$2 \times  {10^{ - 7}}\;\Omega-m$
AIPMT 1994, Medium
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