A __________ surface has the maximum thermal emissivity out of the following.

Related MCQs

• The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2 . The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2 .K4 )
• Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
• 40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is
• The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
• In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
• When a body is in thermal equilibrium with its surroundings, the absorptivity and the emissivity of the body are same. This Law is known as
• The statement that the emissivity and absorptivity of a surface is surrounded by its own temperature are the same for both monochromatic and total radiation, is known as
• Emissivity and absorptivity of a surface are equal for radiation
• The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is
• A wall has two layers A and B, each made of a different material. Both the layers have the same thickness. The thermal conductivity of material of A is twice that of B. Under the thermal equilibrium the temperature difference across the wall is 30?C. The temperature drops in layers A and B will be respectively