Question

what happens to the thermal conductivity of a wall if its thickness is doubled? give a solid reason.

Answer 1

Explanation: 
Thermal conductivity of the material is given by 

k = Q/t * L/A(T1-T2) 

where 
t - time 
Q - Thermal energy 
L - Length (Thickness) 
A - Area 
(T1-T2) - Temperature difference 

From this formula, we can infer that thermal conductivity is directly proportional to the thickness of the material. Therefore, when the thickness doubles, the thermal conductivity becomes double.