How Does a Cyclic Process Work in Thermodynamics?
Opening the discussion with the lines that consider cyclic processes which constitute a very strong and powerful tool in final deductions based on the Second Law. The consideration of two points in configuration space that are infinitesimally close to one another as is represented by 1 and 2 in a particular process of quasistatic that takes a given system from state 1 to state 2. We can say that the heat exchange between the system and surroundings can be given as đrQ1→2 in it.
We ask whether it matters if this quantity is positive or negative. Select a second path that is irreversible that affects the same 1 → 2 change and that literally involves a heat exchange điQ1→2. This path latter is dashed on the diagram which is shown above being a process which is irreversible the path which lies outside the phase space appropriate to quasi-static processes.
By the First Law which is given as đrQ1→2 = dE1→2 – đrW1→2, and điQ1→2 = dE1→2 – điW1→2.
Cyclic Process in Thermodynamics
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In this whole process of passing through a cycle that is working fluid, that is the system may convert heat from a warm source into useful work and even dispose of the remaining heat to a sink of cold. Which is thereby acting as a heat engine. The basic or major conversely that the cycle may be reversed and use work to move heat from a source which is cold and transfer it to a warm sink thereby acting as a heat pump.
At each and every single point in the cycle, we can assume that the system is in thermodynamic equilibrium. So here we can conclude that the cycle is reversible, that is its entropy change is zero as entropy is a state function.
During a cycle that is closed, the system returns to its original thermodynamic state of pressure and temperature. The quantities or we can say the path quantities such as work and heat are process-dependent. For a full and proper cycle for which the system returns to its initial state, the first law of thermodynamics applies the following:
The above clearly states that there is no energy change in the system over the cycle. We denote it as Ein which might be the heat and work that input during the cycle and Eout would be the work and heat output during the cycle. The first law which is of thermodynamics also dictates that the net heat input is equal to the network that is output over a cycle. We can account for heat denoted as Qin as positive and Qout as negative.
What is the Cyclic Process?
Two classes that are of the primary nature of thermodynamic cycles are very powerful cycles and heat can pump the cycles. The cycles of power are cycles that convert some amount of heat input into a work mechanical output, while the pump of heat cycles transfers heat from low to high temperatures by using work that is mechanical as the input.
Work Done in Cyclic Process
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The power of thermodynamic cycles is said to be the basis for the operation of heat engines which can truly supply most of the world's power of electricity and run the vast majority of motor vehicles. The cycle of Power can be organized into two categories: that are the ideal and the real cycles. The encountered cycles which are in real-world devices that are the real cycles are difficult to analyze because of the presence of effect which is complicating friction. And, the absence of sufficient time which is given basically for the establishment of conditions of equilibrium.
For the analysis purpose and design, and at times the model which is idealized ideal cycles are created. Here we can say that the power cycles can also be divided directly according to the type of heat engine they seek to model. The most common cycles which are used to model combustion which are internal engines are the cycle Otto which generally models gasoline engines.
And, the cycle which is of the diesel which has the models diesel engines. The cycles that model combustion engines include the Brayton cycle, which models tribunals of gas, the cycle of Rankine which when models steam turbines the cycle which is Stirling which models hot air engines, and at times the Ericsson cycle which also models hot air engines.
FAQs on Cyclic Process in Physics Explained
1. What is a cyclic process in physics?
A thermodynamic process is defined as cyclic when a system undergoes a series of changes in its state variables (like pressure, volume, and temperature) and ultimately returns to its exact initial state. Because the starting and ending points are identical, the net change in any state function, such as internal energy, is zero for the complete cycle.
2. How is the net work done in a cyclic process calculated using a P-V diagram?
The net work done during a cyclic process is graphically represented by the area enclosed by the loop on a Pressure-Volume (P-V) diagram. The direction of the cycle determines the nature of the work done:
- A clockwise cycle signifies that the system has done positive work on its surroundings (W > 0), as seen in heat engines.
- A counter-clockwise cycle signifies that work has been done on the system by the surroundings (W < 0), as seen in refrigerators.
3. Why is the change in internal energy (ΔU) always zero for a complete cyclic process?
Internal energy (U) is a state function, meaning its value depends only on the current thermodynamic state of the system, not on the path taken to arrive there. Since a cyclic process begins and ends in the exact same state, the initial internal energy (U_initial) is identical to the final internal energy (U_final). Consequently, the net change, ΔU = U_final - U_initial, is always zero.
4. How does the First Law of Thermodynamics apply specifically to a cyclic process?
The First Law of Thermodynamics is expressed as ΔQ = ΔU + W. In a cyclic process, the net change in internal energy (ΔU) is zero. Therefore, the equation simplifies to ΔQ = W. This implies that for an entire cycle, the net heat (ΔQ) supplied to the system is completely converted into the net work (W) done by the system.
5. What is the difference between a cyclic process and a reversible process?
These are distinct concepts:
- A cyclic process is any process where the system returns to its initial state, regardless of how it gets there. It can involve irreversible steps like friction.
- A reversible process is an idealised process that can be retraced along the exact same path in reverse, restoring both the system and surroundings to their original conditions.
6. What are some real-world examples of devices that operate on cyclic processes?
Many common devices rely on thermodynamic cycles to function. Key examples include:
- Heat Engines: The internal combustion engine in a car operates on a repeating cycle (e.g., Otto cycle) to convert the heat from fuel into mechanical work.
- Refrigerators and Air Conditioners: These use a refrigeration cycle to transfer heat from a colder area to a warmer area, which requires an input of work.
7. Is a cyclic process the same as an isothermal process?
No, they are different. An isothermal process is a single process where the temperature is held constant throughout. A cyclic process is a complete sequence of multiple processes (which could include isothermal, adiabatic, etc., steps) that brings a system back to its start. While a cycle can contain an isothermal stage, the entire cycle itself is not isothermal as other properties like pressure and volume must also change.
8. What is the difference between a cyclic and a non-cyclic (acyclic) process?
The primary difference lies in the final state of the system:
- In a cyclic process, the system returns to its original thermodynamic state. As a result, the net change in all state properties like internal energy is zero.
- In a non-cyclic process, the system ends in a different state from where it began. This results in a permanent change in its state properties (e.g., ΔU ≠ 0).
