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What is the rate of energy loss in watt ...

What is the rate of energy loss in watt per square metre through a glass window 5 mm thick if outside temperature is `-20^@ C` and inside temperature is `25^@ C`? (`k_("glass") = 1 W//m K`)

Text Solution

Verified by Experts

Given
` K_("glass") = 1 W // m K`
` T_l = 25^@C `
` T_2 =- 20^@ C`
x= 5 mm `= 5 xx 10^(-3) m`
` therefore T_1 - T_2 = 25 - ( -20 )^@C = 45 K`
we have `P_("cond") = (Q)/(t) = kA (T_1- T_2)/( x)`
` therefore ` The energy loss per square metre ,
` (P_("cond"))/(A) =k (T_1 -T_2)/( x)`
`= 1 W m^(-1) k^(-1) xx 45 K // ( 5 xx 10^(-3)m)`
`= 9xx 10^3 W//m^2`
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