Thermal conductivity of coppe is 9 times that of steel. As shown in figure the temperature difference between ends of copper and steel is 100^(@)C. Find the temperature of their contact surface.

Thermal conductivity of coppe is 9 times that of steel. As shown in fi

1.	Thermal conductivity of coppe is 9 times that of steel. As shown in figure the temperature difference between ends of copper and steel is 100^(@)C. Find the temperature of their contact surface.
Answer» `75^(@)C` `67^(@)C` `33^(@)C` `25^(@)C` Solution :A = same cross - SECTIONAL area `K_(c)=9K_(s)` `T_(1)=100^(@)C` `T_(2)=0^(@)C` Suppose `T_(x)=` TEMPERATURE of contact surface In thermal equilibrium `H_(C)=H_(S)` `:.(K_(c)A(T_(1)-T_(x)))/(L_(1))=(K_(s)A(T_(x)-T_(2)))/(L_(2))` But `L_(1)=18` cm and `L_(2)=6` cm `:.(9K_(s)(100-T_(x)))/(18)=(K_(s)(T_(x)-0))/(6)` `:.3(100-T_(x))=T_(x)` `:.300-3T_(x)=T_(x)` `:.300=4T_(x)` `:.T_(x)=(300)/(4)` `:.T_(x)=75^(@)C`