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Medium:
M1: One end of a rod of length 20cm is inserted in afurnance at 800k. the sides of the rod are
covered with an insulating material and the other end emits radiation like a black body. The temperature of this rod is 150 k in the steady state. The temperature of the surrounding air is 300k. Assuming radiation to be
the only important mode of energy transfer between the surroundings and open end of the rod, find the thermal conductivity of the rod
Stefan's const = 6.0 x 10-8 w/m2k4
Solution:
K = 74 w/mK
M:2 A closed cylinder box made of perfectly insulating materials has walls of thickness 8cm and the only way for the heat to enter or lic plugs each of cross sectional area 12cm
2
and length 8cm fixed in the opposite walls of the box as shown in figure. the outer surface A is kept at 100c while the outer surface B of other plug is kept at 4c. K of the material of the plugs is 0.5 cal/s/c/cm. The source of energy generating 36 cal/s is enclosed inside the box. Find the equilibrium temperature of the inner surface of the box assuming that it is same at all points on the inner surface.
Solution: Q : Temperature of inner surface
=> Q = 76
0
c
M3: Find temperature as a function of radius r in case of spherical shell. inner and outer surface temperature being Q
1
and Q
2
respectively.
Solution:
Considering a shell r and thickness dr
Q = Q
1
=
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