JEE Main202127 Aug 2021Morning ShiftPhysicsThermal Properties of MatterActual
A rod C D of thermal resistance 10 . 0 KW - 1 is joined at the middle of an identical rod A B as shown in figure. The ends A ,   B and D are maintained at 200 ° C , 100 ° C and 125 ° C respectively. The heat current in C D is P   W . The value of P is
Correct answer
0
Step-by-step solution
Q A C + Q D C = Q C B K A ( 200 - t ) ℓ 2 + K A ( 125 - t ) ℓ = ( t - 100 ) K A ℓ 2 400 - 2 t + 125 - t = 2 t - 200 725 = 5 t t = 145 º C Q C D = K A ( 145 - 125 ) ℓ = 20 ℓ K A = 2   W