The thermal conductivity of brick is 1.7 W m-1k-1 and that of cement i

1.	The thermal conductivity of brick is 1.7 W m-1k-1 and that of cement is 2.9 W m-1k-1 . What thickness of cement will have same insulation as the brick of thickness 20 cm.
Answer» Given : K_B = 1.7 W m⁻¹K⁻¹ K = 2.9 W m⁻¹K⁻¹ d = 20 cm d_c = ? From formula the heat flow is given by Q=KA\(\frac{Δ\theta}{d}t\) For same insulation by the brick and the cement, Q, A, ∆θ and t don’t change. Hence should be a constant. or \(\frac{K_{\theta}}{d_{\theta}}\)=\(\frac{K_{c}}{d_{c}}\) or d_c=\(\frac{K_{C}}{K_{B}}d_{B}\) =\(\frac{2.9}{1.7}\times20=34.12cm\)

The thermal conductivity of brick is 1.7 W m-1k-1 and that of cement is 2.9 W m-1k-1 . What thickness of cement will have same insulation as the brick of thickness 20 cm.

Answer»

Given :

K_B = 1.7 W m⁻¹K⁻¹

K = 2.9 W m⁻¹K⁻¹

d = 20 cm

d_c = ?

From formula the heat flow is given by

Q=KA\(\frac{Δ\theta}{d}t\)

For same insulation by the brick and the cement, Q, A, ∆θ and t don’t change. Hence should be a constant.

or \(\frac{K_{\theta}}{d_{\theta}}\)=\(\frac{K_{c}}{d_{c}}\)

or d_c=\(\frac{K_{C}}{K_{B}}d_{B}\)

=\(\frac{2.9}{1.7}\times20=34.12cm\)