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The transfer of heat is termed as the transfer of thermal energy from one body to another body when they come into physical contact or through thermal radiation. Either case is, the temperature changes is the flow of heat from the body at higher temperature towards the body at the lower temperature until a situation of thermal equilibrium is achieved. Newton came up with a formula to determine and explain the rate of cooling, i.e., the transfer of heat from one body to another. This law came to be known as the law of cooling, where the loss of heat from the body is directly proportional to the temperature difference between the body and the surrounding.
WHAT IS TEMPERATURE:
The temperature is termed as the physical quantity for the measure of the hotness and coldness of an object. The temperature depends upon the thermal energy that is stored within a body. This storage of energy leads to the existence of heat, the flow of energy, the flow of heat, etc. The instrument that is used for measuring temperature is a thermometer, and it is measured in three distinctive units, i.e., degree Celsius, degree Fahrenheit, and degree Kelvin. The lowest temperature that is recorded as the absolute temperature is called absolute zero. At this temperature, there is no energy left within the body that can cause a temperature change.
Temperature is one of the important aspects in the field of science, which plays an active role in astronomy, medicine, geography, biology, metallurgy, etc.
HEAT TRANSFER:
As it is a well-known fact that each of the matter stores a particular amount of energy. This energy causes a change in the temperature of the body. However, this energy is transferred from one body to another, which is termed heat transfer. This movement of the heat from one body to another body is done by three mechanisms: thermal conduction, thermal convection, and thermal radiation. These are the three-phase changes where the transfer of energy takes place within the body on the basis of physical contact. As per the given law, the Second law of thermodynamics is termed as energy flowing from the object at a higher temperature to the body at a lower temperature until a situation of thermal equilibrium is achieved. The unit of measurement of heat is joules. Therefore, the unit of rate of heat transfer is joules per second.
NEWTON’S LAW OF COOLING:
The transfer of heat takes place within the body until a condition of thermal equilibrium is achieved, i.e., the temperature of the body is equal to the temperature of the surrounding. Newton came forward with a law that explains the aspects of the transfer of heat from one body to the other. This law came to be known as the law of cooling, which states that the loss of heat from the body is directly proportional to the temperature difference between the body and its surroundings. Assuming the transfer of heat from one body to another through the mechanism of thermal radiation and considering time as an important aspect in the transfer of the heat, Newton’s law of Cooling is expressed as,
METHODS TO APPLY THE LAW:
For the application of the law of cooling, the rate of cooling, i.e., the loss of heat is considered. Mathematically, it is expressed as,
dQ/dt
Moreover, the rate of change in temperature is considered between the body and the surroundings, which is expressed as,
[q-qs] (where q is the temperature of the body and qs is the temperature of the surrounding)
According to Newton’s law of cooling, both equations are directly proportional to each other,
dQ/dt ∝ [q-qs]
dQ/dt=k [q-qs]
Here k is termed as the constant.
However, the temperature difference between the body can be expressed in terms of the initial and final temperature of the body.
q=(qi-qf)/2
Here, qi is the initial temperature of the body, and qf is the final temperature of the body.
LIMITATION OF THE NEWTON’S LAW OF COOLING:
There are several limitations to Newton’s law of cooling. Some of them are.
- The temperature difference between the body as well as the given surrounding must be of a small variation.
- The transfer of the heat is assumed to be through the mechanism of thermal radiation.
- One of the basic limitations that were implemented over Newton’s law of cooling is that the rate of change in temperature must be at a constant rate.
CONCLUSION:
Newton’s law of cooling is the direct representation of the constant at which the transfer of heat takes place within the body until the condition of thermal equilibrium is achieved. Newton’s law of cooling states that the loss of heat from the body is directly proportional to the temperature difference between the body and the surrounding. The transfer of heat takes place within three distinctive mechanisms, namely, thermal conduction, thermal convection, and thermal radiation. However, it is assumed that the heat transfer is undertaken through thermal radiation for the implementation of Newton’s law of cooling. It is considered one of the limitations that were imposed on Newton’s law of cooling.
