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NTA Abhyas JEE Main2020PhysicsThermal Properties of MatterPractice

Two spheres of radii 8 cm and 2 cm are cooling. Their temperatures are 127 ℃ and 527 ℃ respectively. The ratio of energy radiated by them in the same amount of time is

Options

  1. A0 . 06
  2. B0 . 5
  3. C1
  4. D2

Correct answer

C. 1

Step-by-step solution

Total energy radiated from a body Q = A ε σ T 4 t or Q t ∝ A T 4 Q t ∝ r 2 T 4 ( ∵ A = 4 π r 2 ) Q 1 Q 2 = r 1 r 2 2 T 1 T 2 4 = 8 2 2 273 + 127 273 + 527 4 = 1

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