Question

A liquid-nitrogen container is made of a `1-cm` thick styrofoam sheet having thermal conductivity `0.025Js^(-1)m^(-1)`^(@)C^(1)` . Liquid nitrogen at 80K is kept in it. A total area of `0.80m^(-2)` is in contcet with the liquid nitrogen. The atmospheric temperature is `300K` . Calculate the rate of heat flow from the atmosphere to the liquid nitrogen.

Answer 1

Correct Answer - D
`d=1cm=0.01m A=0.2 m^(2)`
`(T_(1))=300^(@)C`,brgt``(T^(2))=80^(@)C`,brgt`K=0.025W//m-^(@)C`
`(Q)/(T)=(kA(T_1-T_2))/(l)`
`(0.025xx0.2xx(300-80))/0.01`
`=110 watt.`