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10.2 , transmission of heat — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics10.2 , transmission of heat1 Mark
MCQ
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
    $\frac{4l}{{7ka}}$
  • ✓
    $\frac{l}{{2ka}}$
✓

Answer

Correct option: D.
$\frac{l}{{2ka}}$
d
Let $\mathrm{R}=\frac{1}{\mathrm{K}} \cdot \frac{l}{\mathrm{a}}$

$R_{e q}=\frac{R}{2}=\frac{1}{2}\left(\frac{\ell}{k a}\right)$

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