Two identical metal wires of thermal conductivities $K _{1}$ and $K _{2}$ respectively are connected in series. The effective thermal conductivity of the combination is
Two identical metal wires of thermal conductivities $K _{1}$ and $K _{2}$ respectively are connected in series. The effective thermal conductivity of the combination is
- A
$\frac{2 K _{1} K _{2}}{ K _{1}+ K _{2}}$
- B
$\frac{ K _{1}+ K _{2}}{2 K _{1} K _{2}}$
- C
$\frac{ K _{1}+ K _{2}}{ K _{1} K _{2}}$
- D
$\frac{ K _{1} K _{2}}{ K _{1}+ K _{2}}$
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