An object has the shape of cubical box of side $$10cm,$$ with no top cover. The box is placed inside a room whose dimensions are much larger than those of the box. All the five surfaces of box are at a temp of $${500^ \circ }C$$ and have an emissivity of $$0.6.$$ The walls of the room are at $${25^ \circ }C$$ and have an emissivity of $$0.4.$$ All these surfaces can be assumed to be diffuse-gray. Find the net radiative heat loss from the inner surface of the box to the walls of the room.
Stephen Boltzmann constant $$5.67 \times {10^{ - 8}}\,\,W/{m^2}{K^4}$$. View factor between two parallel square plates placed directly opposite to each other is $$0.2$$

A diffuse radiation surface has

Biot number signifies

Match the property with their units

Property
$$A.$$ Bulk modulus
$$B.$$ Thermal conductivity
$$C.$$ Heat transfer coefficient
$$D.$$ Heart flow rate

Units
$$1.$$ $$W/s$$
$$2.$$ $$N/{m^2}$$
$$3.$$ $$N/{m^3}$$
$$4.$$ $$W$$
$$5.$$ $$W/mK$$
$$6.$$ $$W/{m^2}K$$