Two metal wires of identical dimensions are connected in series. If $\sigma_{1}$ and $\sigma_{2}$ are the electrical conductivities of the metal wires respectively, the effective conductivity of the combination is

  • A
    $\sigma_{1}+\sigma_{2}$
  • B
    $\frac{\sigma_{1} \sigma_{2}}{\sigma_{1}+\sigma_{2}}$
  • C
    $\frac{2 \sigma_{1} \sigma_{2}}{\sigma_{1}+\sigma_{2}}$
  • D
    $\frac{\sigma_{1}+\sigma_{2}}{2 \sigma_{1} \sigma_{2}}$

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