Q.

Two plates A and B have thermal conductivities 84 W m-1K-1 and 126 W m-1K-1 respectively. They have same surface area and same thickness. They are placed in contact along their surfaces. If the temperatures of the outer surfaces of A and B are kept at 100°C and 0°C respectively, then the temperature of the surface of contact in steady state is ________ C.                 [2023]


Ans.

(40)

Let the temperature of the contact surface is T, then

HA=HB

KAA(TA-T)L=KBA(T-TB)L

84(100-T)=126(T-0)

2(100-T)=3T

 T=40°C