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Two metal wires of identical dimen...

Two metal wires of identical dimensions are connected in series if `sigma_(1)` and `sigma_(2)` are the conductivity of the metal wire respectively the effiective conductivity of the combination is

A

`(sigma_1sigma_2)/(sigma_1+sigma_2)`

B

`(2sigma_1sigma_2)/(sigma_1+sigma_2)`

C

`(sigma_1+sigma_2)/(2sigma_1sigma_2)`

D

`(sigma_1+sigma_2)/`(sigma_1sigma_2)`

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