What length of the wire of specific resistance $48 \times {10^{ - 8}}\,\Omega \,\,m$ is needed to make a resistance of $4.2 \, \Omega$  .............. $m$ (diameter of wire = $0.4\, mm$)
  • A$4.1$
  • B$3.1$
  • C$2.1$
  • D$1.1$
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