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A steel farme (K=45Wm^(-1)^(@)C^(-1) of ...

A steel farme `(K=45Wm^(-1)`^(@)C^(-1)` of total length `60cm` and cross section area `0.02cm^(2)` , Forms three side of a square. The free ends are maintained at `20^(@)C` and `40^(@)C` . Find the rate of heat flow through a cross section of the frame.

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The correct Answer is:
C
`K=45W//m-^(@)C,`
`1=60 cm=60xx10^(-2)m`
`A=0.2 cm^(2)=0.2xx10^(-4)m^(2)`
Rate of heat flow,
`(kA(T_1-T_2))/(l)=(45xx0.2xx10^(-4)xx20)/(60xx10^(-2))`
`=30xx10^(-3)=0.03W`
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