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Heat Transfer. — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsHeat Transfer.5 Marks
Question
A steel frame $(\text{K}=45\text{Wm}^{-1}{^{\circ}}\text{C}^{-1})$of total length 60cm and cross sectional area $0.20cm^2$, forms three sides of a square. The free ends are maintained at $20^\circ C$ and $40^\circ C$. Find the rate of heat flow through a cross section of the frame.
✓

Answer



$\text{K}=45\text{w/m-}^\circ\text{C}$
$\ell=60\text{cm}=60\times10^{-2}\text{m}$
$\text{A}=0.2\text{cm}^2=0.2\times10^{-4}\text{m}^2$
Rate of heat flow,
$=\frac{\text{KA}(\theta_1-\theta_2)}{\ell}$
$=\frac{45\times0.2\times10^{-4}\times20}{60\times10^{-2}}$
$=30\times10^{-3}=0.03\text{w}$

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