PQ is a fully-lagged metal bar, containing a section XY of a material of lower thermal conductivity. The thermal conductivities of the two materials are independent of temperature. Ends P and Q are maintained at different temperature.
In the steady , the temperature difference across XY would be independent of :

Options

A. The temperature difference between P and Q
B. The metal of which the bar is made
C. The thickness of the section XY
D. The distance of the section XY from the end P

Answer

D

Explanation

As the metal bar is of uniform cross section, through outthemetal barin steady state the temperature gradient will be constant hence for a given thickness of XY at every location in metal bar its temperature difference will be constant.