A Detailed Explanation on the Limitation of First Law of Thermodynamics

The laws of thermodynamics are straightforward to explain. What if I told you that the human body is subject to the laws of thermodynamics? When we’re in a room with a lot of people, we start to sweat and feel heated, and the perspiration gets extreme if the room is small. This occurs because your body is attempting to cool itself, and as a result, heat is transferred from your body in the form of sweat.’ The first law of thermodynamics entails this situation.

First Law of Thermodynamics

An isolated system’s total energy is constant according to the first law of thermodynamics, which is stated as follows: Energy has the ability to transition from one form to another, but it cannot be created or destroyed in any way.

According to this law, some of the heat supplied to the system is utilised to change the internal energy, while the remainder is employed by the system to perform work. Mathematically,

ΔQ=ΔU+ΔW

where,

Q is the amount of heat that is given to the system.

W denotes the amount of work completed by the system.

A change in the system’s internal energy is denoted by the symbol U.

Whenever Q is positive, it indicates that there is a net heat transfer into the system; when W is positive, it indicates that the system is performing work. As a result, positive Q contributes energy to the system, whereas positive W depletes energy from the system

Alternatively, U=QW can be used to express it.

To put it another way, when heat is introduced into the system, internal energy tends to increase, and vice versa.

Cycles of Thermodynamic Energy

The overall amount of energy in an isolated system remains constant. At the end of a thermodynamic cycle, the system’s net heat input equals the system’s net work output. The batteries we employ, for example, are capable of converting chemical energy into electrical energy. Electric bulbs, on the other hand, translate electrical energy into light energy.

It is not just the starting and final states of a gas that determine how much work can be done on or by it; it is also the process that leads to the final state that determines how much work can be done. Additionally, the quantity of heat carried into or out of a gas relies on the initial and final states of the gas, as well as the mechanism that leads to the formation of the final state.

Internal energy is just another sort of energy, such as the potential energy of an object at a certain height above the surface of the earth or the kinetic energy of an object in motion. A thermodynamic system’s internal energy converts into either kinetic or potential energy in the same way as potential energy translates into kinetic energy while maintaining the total energy of the system. This is known as entropy conversion. Internal energy can be stored in the system in the same way as potential energy can. In spite of the fact that the first law of thermodynamics allows for a large number of potential states of a system to exist, only a few of these states have been observed in nature.

Limitations to the First Law of Thermodynamics.

• The first law of thermodynamics has a problem in that it does not specify the direction in which heat is travelling through space, which is a significant limitation.
• It makes no distinction between whether the process is a spontaneous process or whether it is not a spontaneous process
• Going backwards in time is not a practical option. In real-world practice, the heat does not completely convert to work as efficiently as it should be. In the event that it had been possible to convert all of the heat into work, humans would have been able to move ships across the ocean by extracting heat from the water of the ocean.

Conclusion

The following are some of the implications of the first law of thermodynamics:

It is established by the first law of thermodynamics that there is a relationship between heat and work.

Neither Work nor Heat can be distinguished from one another.

If any system gains or loses energy, the exact corresponding amount of energy in the surrounding environment will be lost or acquired, respectively.

Applied heat is always equal to the sum of the work done and the change in internal energy, unless otherwise specified.

When a system is isolated, the energy is always the same.