Breaking Down The First Law Of Thermodynamics Equation

The First Law of Thermodynamics, an extension of the law of conservation of energy, states that energy can neither be created nor destroyed, only altered in form. The law is based on the principle that the total energy of a system remains constant even if it is converted from one form to another. This means that the total energy entering a system is equal to the total energy leaving the system, plus the change in the system's internal energy.

The First Law of Thermodynamics can be applied to three types of systems: closed, open, and isolated. A closed system allows energy transfer but disallows mass transfer, an isolated system prohibits both energy and mass transfer, and an open system permits both. The law is particularly useful for understanding the exchange of energy between a system and its surroundings.

The equation representing the First Law of Thermodynamics for an open system is:

ΔE_system = Q_in - W_out + m_in e_in - m_out e_out

Here, ΔE_system refers to the change in internal energy of the system, Q_in is the heat entering the system, W_out is the work done by the system on its surroundings, and m_in e_in and m_out e_out represent the energy entering and leaving the system by mass, respectively.

The Law of Conservation of Energy

The First Law of Thermodynamics distinguishes between two primary forms of energy transfer: heat and thermodynamic work. These transfers of energy modify a thermodynamic system that contains a constant amount of matter. The law also defines the internal energy of a system, taking into account the balance of heat and work within the system.

The internal energy of a system refers to the total energy within a thermodynamic system, including the kinetic and potential energy of molecules and any energy associated with the system's internal structure. In an isolated system, the sum of all forms of energy remains constant.

The First Law of Thermodynamics can be applied to open systems, which are systems that exchange both energy and mass with their surroundings. In an open system, energy can enter or leave, and it can come in various forms such as heat, work, and mass. The law helps us understand the complex exchange of energy between the system and its surroundings.

The Energy Balance for an Open System states that the total energy entering a system should be equal to the total energy leaving the system, plus any change in the system's internal energy. This can be represented mathematically as:

ΔE_system = Q_in - W_out + m_in * e_in - m_out * e_out

Where:

• ΔE_system refers to the change in internal energy of the system
• Q_in is the heat entering the system
• W_out is the work done by the system on its surroundings
• M_in e_in is the energy entering the system via mass
• M_out e_out is the energy leaving the system via mass

This equation highlights that energy can only be converted from one form to another, supporting the principle of the Law of Conservation of Energy.

Heat and Work

The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, but can be transferred from one form to another. The total energy of a system remains constant, even if it is converted from one form to another.

The first law of thermodynamics distinguishes two principal forms of energy transfer: heat and work. Heat is the transfer of thermal energy between two bodies at different temperatures. Work is the force used to transfer energy between a system and its surroundings and is needed to create heat and the transfer of thermal energy.

The first law of thermodynamics can be expressed mathematically as:

• ΔU = q + w
• Where ΔU is the total change in internal energy of a system
• Q is the heat exchanged between a system and its surroundings
• W is the work done by or on the system

Work can also be calculated as the negative external pressure on the system multiplied by the change in volume:

• W = -pΔV
• Where p is the external pressure on the system
• ΔV is the change in volume

The internal energy of a system would decrease if the system gives off heat or does work. Therefore, the internal energy of a system increases when heat increases or when work is done on the system. Any work or heat that goes into or out of a system changes the internal energy.

Since energy is never created or destroyed, the change in internal energy always equals zero. If energy is lost by the system, it is absorbed by the surroundings, and vice versa. This can be expressed as:

ΔUsystem = -ΔUsurroundings

An example of the first law of thermodynamics in action is a heat engine, where thermal energy is converted into mechanical energy, and vice versa. Heat engines are mostly categorised as open systems.

Internal Energy

The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, only altered in form. This means that the total energy of a system remains constant, even if it is converted from one form to another. The first law of thermodynamics is also sometimes referred to as the law of conservation of energy.

The first law of thermodynamics relates to heat, internal energy, and work. It states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.

The first law of thermodynamics can be expressed mathematically as:

ΔU = Q - W

Where:

• ΔU is the change in internal energy of the system
• Q is the heat given or lost
• W is the work done on the gas

The internal energy of a system increases or decreases depending on the work interaction that takes place across its boundaries. If work is done on the system, the internal energy increases, and if work is done by the system, the internal energy decreases. Any heat interaction between the system and its surroundings also changes its internal energy. However, since energy remains constant (from the first law of thermodynamics), the total change in internal energy is always zero.

The first law of thermodynamics can be applied to both closed and open systems. For a closed system, the work done is the product of the constant external pressure on the system and the change in volume that occurs due to the applied pressure. In contrast, an open system can exchange both energy and matter with its surroundings.

The first law of thermodynamics is of enormous interest and has been validated experimentally many times. It provides a definition of internal energy and introduces an additional state variable, enthalpy. However, it has some limitations. For example, it does not tell us about the direction of heat flow and fails to explain why heat cannot be spontaneously converted into work. This is addressed by the second law of thermodynamics, which provides the criterion for the feasibility of various processes.

Energy Transfer

The First Law of Thermodynamics, also known as the Law of Conservation of Energy, states that energy can neither be created nor destroyed, but it can be transferred from one form to another. This law applies to three types of systems: closed, open, and isolated.

A closed system allows energy transfer but disallows mass transfer. The internal energy of a closed system remains constant, and any energy lost by the system will be absorbed by its surroundings, and vice versa. The change in internal energy of a closed system is given by the equation:

ΔU = Q - W

Where:

• ΔU is the change in internal energy of the system
• Q is the heat added to the system
• W is the work done on the system

An open system permits the transfer of both energy and mass across its boundaries. The First Law of Thermodynamics for an open system can be represented by the equation:

ΔE_system = Q_in - W_out + m_in * e_in - m_out * e_out

Where:

• ΔE_system is the change in internal energy of the system
• Q_in is the heat entering the system
• W_out is the work done by the system on its surroundings
• M_in e_in is the energy entering the system via mass
• M_out e_out is the energy leaving the system via mass

This equation demonstrates that energy can neither be created nor destroyed in an open system; it can only be converted from one form to another. This principle is fundamental to various engineering applications, such as heat transfer and fluid flow.

Energy Balance for an Open System

The First Law of Thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. It distinguishes two principal forms of energy transfer: heat and thermodynamic work. The law also defines the internal energy of a system, which is a state function that accounts for the balance of heat and work in the system.

The First Law of Thermodynamics for an open system deals with three types of systems: closed, open, and isolated. A closed system allows energy transfer but not mass transfer. An isolated system prohibits both energy and mass transfer, while an open system permits both.

The Energy Balance for an Open System is a mathematical representation of the First Law of Thermodynamics for an open system. It states that the total energy entering a system is equal to the total energy leaving the system, plus the change in the system's internal energy. This can be represented by the equation:

ΔEsystem = Qin - Wout + minein - mouteout

Where:

• ΔEsystem refers to the change in internal energy of the system.
• Qin is the heat energy entering the system.
• Wout is the work done by the system on its surroundings.
• Minein is the energy entering the system via mass.
• Mouteout is the energy leaving the system via mass.

This equation illustrates the principle that energy cannot be created or destroyed, only converted from one form to another. This principle is fundamental to various phenomena, such as heat transfer and fluid flow in engineering applications.

The Energy Balance for an Open System is a crucial concept in understanding the behaviour of open systems and plays a significant role in various scientific and engineering disciplines.

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