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Question
A uniform slab of dimension 10 cm × 10 cm × 1 cm is kept between two heat reservoirs at temperatures 10°C and 90°C. The larger surface areas touch the reservoirs. The thermal conductivity of the material is 0.80 W m−1 °C−1. Find the amount of heat flowing through the slab per minute.
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Solution
Given:
Thermal conductivity of the material, k = 0.80 W m-1 °c-1
Area of the cross section of the slab, A = 100 cm2 = 10-2 m2
Thickness of the slab, Δx = 1 cm = 10 -2 m
`"Rate of flow of heat" ="Temperature difference" / "Thermal resisstance"`
`⇒ (ΔQ)/(Δt) = (ΔT)/((Δx)/(kA)`
`(ΔQ)/(Δt) = ((90 - 10 ) k.A)/(Δx)`
`(ΔQ)/(Δt) = ((80) xx 0.8 xx 10^-2)/(Δx)1`
`(ΔQ)/(Δt)= 64 J //s`
`(ΔQ)/(Δt) = 64xx60 = 3840 J//min`
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