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Newton’s Law of Cooling - Class 11 Physics Notes, Explanation & Applications

Introduction:

Newton's Law of Cooling describes how the rate of cooling of an object is proportional to the difference in temperature between the object and its surroundings. This is an important concept in thermodynamics and can be applied to various real-life scenarios, such as cooling of coffee, room temperature adjustments, or body temperature stabilization.




Key Points of Newton's Law of Cooling:


1. Statement of Newton's Law of Cooling:

The rate of change of temperature of an object is proportional to the difference between its own temperature and the ambient temperature (temperature of its surroundings).


2. Differential Equation:

 

3. Solution to the Differential Equation:


4. Graphical Representation:

-A plot of temperature T(t) vs. time t typically shows an exponential decay curve, asymptotically approaching Tenv.

  -This graph demonstrates that as time progresses, the temperature difference decreases, resulting in a slower rate of cooling.


5. Limitations of Newton's Law of Cooling:

  -It is most accurate when the temperature difference is not too large.

  -The law assumes a constant ambient temperature and neglects the effects of heat radiation and convection, which may affect the cooling rate in real-life situations.


Read Also: Dimensions of Physical Quantities for Class 11 Physics Notes


6. Applications:

Forensic Science: Estimating the time of death by measuring body temperature.

Food Industry: Predicting cooling times for food and beverages.

Meteorology: Modeling temperature changes of surfaces exposed to varying ambient temperatures.


Conclusion:

Newton's Law of Cooling provides a valuable insight into how objects exchange heat with their surroundings. It shows that the cooling rate is directly proportional to the temperature difference between the object and its environment, leading to an exponential decline in temperature over time. This principle is crucial in various fields, from forensics to engineering, as it allows predictions about temperature changes based on environmental conditions. However, its accuracy diminishes when temperature differences are extreme or when other factors, such as radiation and convection, significantly affect the cooling process.

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