A black rectangular surface of area A emits energy E per second at 27 ° C . If length and breadth are reduced to 1 3 rd of initial value and temperature is raised to 327 ° C , then energy emitted per second becomes

Question

A black rectangular surface of area A emits energy E per second at 27 ° C . If length and breadth are reduced to 1 3 rd of initial value and temperature is raised to 327 ° C , then energy emitted per second becomes, 4 E 9, 7 E 9, 10 E 9, 16 E 9

MARKS App · Accepted Answer

E = e σ . A T 4 - T 0 4 a n d A = l b When l and b changes to l 3 and b 3 A → A 9 E ′ E = A ′ A 327 + 273 4 27 + 273 4 ∴ E ′ E = 1 9 600 300 4 ∴ E ′ = 1 9 × 2 4 × E E ′ = 16 E 9

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