Correct option (b) Q/16
Explanation:
The amount of heat flows in time t through a cylindrical metallic rod of length L and uniform area of cross-section A(=πR2) with its ends maintained at temperatures T1 and T2 (T1 >T2) is given by
where K is the thermal conductivity of the material of the rod.
Area of cross-section of new rod
Now. the amount of heat flows in same time t in the new rod with its ends maintained at the same temperatures T1 and T2 is given by
Substituting the values of A' and L' from equations (ii) and (iii) in the above equation, we get