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A plate having 10 cm2 area each side is hanging in the middle of a room of 100 m2 total surface area. The plate temperature and emissivity are respectively 800 K and 0.6. The temperature and emissivity value for the surfaces of the room are 300 K and 0.3 respectively. Boltzmann's constant σ = 5.67 × 10-8 W/m2K4. The total heat loss from the two surfaces of the plate is
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- 13.66 W
- 27.32 W
- 27.87 W
- 13.66 MW
Correct Option: B
Heal loss from one surface of the plate,
Putting A1 = 10 × 10–4 m2, T1 = 800
ε1 = 0.6 T2 = 300
A2 = 100 m2
ε2 = 0.3
∴ Heat loss from both the surfaces
= 2 Qnet
= 2 × 13.66 = 27.32 W
