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Grade 11Thermal Physics

A wall has two layers A and B each made of different materials. the layer A is 10 cm thick and B is 20 cm thick. the thermal conductivity of A is thirce that of B. Under thermal equilibrium, temperature across the wall is 35 degree celcius. The difference of temperature across the layer A is a) 30 degree celcius. b) 14 degree celcius. c) 8.75 degree celcius. d) 5 degree celcius.

Profile image of Arnab Mandal
14 Years agoGrade 11
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2 Answers

Profile image of Swapnil Saxena
14 Years ago

If the walls are in series then the heat currents established in both thew walls should be equal.

Let the temp. at A=0(say) , B=35( to maintain the temp. difference of 35 b/w the walls) and T (say across the layer)

= dQ1/dt =dQ2/dt

= (3K)A(T-0) / 10 = (K)A(35-T) / 20

= (6K)A(T)= (K)A(35-T)

= (6K) = (35-T)

=>7T=35

=> T= 5 -----------(ans)

Profile image of ankit singh
5 Years ago

let the temp. at A=0(say) , B=35( to maintain the temp. difference of 35 b/w the walls) and T (say across the layer)

= dQ1/dt =dQ2/dt

= (3K)A(T-0) / 10 = (K)A(35-T) / 20

= (6K)A(T)= (K)A(35-T)

= (6K) = (35-T)

=>7T=35

=> T= 5 -----------(ans)

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