Question

13. A composite rod made of three rods of equal length and cross section as shown in the fig. The thermal conductivities of the materials of the rods are K/2, 5K and K respectively. The end A and B are at constant temperatures. All heat entering the face A goes out of the end B there being no loss of heat from the sides of the bar. The effective thermal conductivity of the bar is

​A B











K/2 5K K

(A) 15K/16
(B) 6K/13
(C) 5K/16
(D) 2K/13

​14. A black metal foil is warmed by radiation from a small sphere at temperature "T" and at a distance "d". It is found that the power received by the foil is P. If both the temperature and distance are doubled, the power received by the foil will be:
(A) 16P
(B) 4P
(C) 2P
(D) p

Answer 1

16pon you have posted