Two metal wires of identical dimensions are connected in series. If `sigma_(1)` and `sigma_(2)` are the conductivities of the metal wires respectively, the effective conductivity of the combination is 

Options

A. `(sigma_(1)sigma_(2))/(sigma_(1)+sigma_(2))`
B. `(2sigma_(1)sigma_(2))/(sigma_(1)+sigma_(2))`
C. `(sigma_(1)+sigma_(2))/(2sigma_(1)sigma_(2))`
D. `(sigma_(1)+sigma_(2))/(sigma_(1)sigma_(2))`

Answer

B