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Concepts Of Physics MCQ Edition [Volume 2]PhysicsHeat Transfer

A metal block having a heat capacity of 80 J ^ C ⁻¹ is located in a room at 20^ C and is heated electrically. Once the temperature attains 30^ C , the heater is turned off. Just after the heater is turned on, the block's temperature increases at a rate of 2^ C s ⁻¹ , and just after it is turned off, the temperature decreases at a rate of 0.2^ C s ⁻¹ . Assuming Newton's law of cooling is valid, determine the power rad

Options

  1. A16 W
  2. B32 W
  3. C20 W
  4. D8 W

Correct answer

A. 16 W

Step-by-step solution

The rate of heat loss (power radiated) by the block immediately after the heater is turned off is given by: P = C (- dT dt ) Given the heat capacity C = 80 J ^ C ⁻¹ and the rate of cooling just after the heater is turned off is (- dT dt ) = 0.2^ C s ⁻¹ . Substituting the given values: P = 80 0.2 = 16 W

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