A brick wall having a thickness of 24 cm has an inner surface temperature of 25°C and an outer surface temperature of 5°C. The rate of heat loss through per square metre of the wall (thermal conductivity 0.15 J/ (s.m.K)) is:

Correct option is A

By formula
Where,
dq = Change in heat, dt = per unit time
h = thermal conductivity,
dl - width of wall
A = area across wall
T₁ and T₂ Temperature across wall
Given, –
Thermal conductivity h = 0.15J/(s.m.k)
width (dL) = 24 cm = 0.24m
Area across wall (A) = 1m²
Now,
Heat transfer rate = 12.5