Concepts Of Physics MCQ Edition [Volume 2]
- Exam
- Concepts Of Physics MCQ Edition [Volume 2]
- Subject
- Physics
- Chapter
- Heat Transfer
Concepts Of Physics MCQ Edition [Volume 2] · Physics · Heat Transfer
A metal block having a heat capacity of 80 J ^ ^ ^ ^ -1 is located...
A metal block having a heat capacity of 80 \text{ J }^{}^{{}^{\circ}}\textC^{-1} is located in a room at 20^{}^{{}^{\circ}}\text{C} and is heated electrically. Once the temperature attains 30^{}^{{}^{\circ}}\text{C}, the heater is turned off. Just after the heater is turned on, the block's temperature increases at a rate of 2^{}^{{}^{\circ}}\text{C s}^{-1}, and just after it is turned off, the temperature decreases at a rate of 0.2^{}^{{}^{\circ}}\text{C s}^{-1}. Assuming Newton's law of cooling is valid, determine the power radiated by the block immediately after the heater is turned off.
Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
The rate of heat loss (power radiated) by the block immediately after the heater is turned off is given by:
\left(-\dfrac{dT}{dt}\right)
Given the heat capacity and the rate of cooling just after the heater is turned off is 0.2^\circ\text{C s}^{-1}P = 80 \times 0.2 = 16 \text{ W}
\left(-\dfrac{dT}{dt}\right)
Given the heat capacity and the rate of cooling just after the heater is turned off is 0.2^\circ\text{C s}^{-1}P = 80 \times 0.2 = 16 \text{ W}