Find effective thermal resistance between $A$ & $B$ of cube made up of $12$ rods of same dimensions and shown given thermal conductivity. [ $l =$ length of rod, $a =$ cross section area of rod]
A$\frac{l}{{ka}}$
B$\frac{2l}{{ka}}$
C$\frac{4l}{{7ka}}$
D$\frac{l}{{2ka}}$
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D$\frac{l}{{2ka}}$
d Let $\mathrm{R}=\frac{1}{\mathrm{K}} \cdot \frac{l}{\mathrm{a}}$
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