A wall consists of alternating blocks of length $d$ and coefficient of thermal conductivity $K_{1}$ and $K_{2}$ respectively as shown in figure. The cross sectional area of the blocks are the same. The equivalent coefficient of thermal conductivity of the wall between left and right is
A wall consists of alternating blocks of length $d$ and coefficient of thermal conductivity $K_{1}$ and $K_{2}$ respectively as shown in figure. The cross sectional area of the blocks are the same. The equivalent coefficient of thermal conductivity of the wall between left and right is
- [NEET 2017]
- A
$\frac{{2{K_1}{K_2}}}{{{K_1} + {K_2}}}$
- B
$\frac{{{K_1} + {K_2}}}{3}$
- C
$\;\frac{{{K_1}{K_2}}}{{2({K_1} + {K_2})}}$
- D
$\;\frac{{{K_1} + {K_2}}}{2}$
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