Internal energy of a gas remains unchanged in
(I) an isothermal process
(II) an adiabatic process
(III) a reversible process
(IV) a cyclic process
Which of the these are true?
Cyclic process \(\quad \Delta U=0\) so elnternal energy remains constant. Isothermal process \(T=\) const. so \(U=\) constant. So Internal energy of a gas remains constant in an Isothermal and cyclic process.
A transition from one kind of equilibrium microstate to another kind of system is a part of a thermodynamic process. The system's starting and final states can be used to understand the process.
The system's volume, temperature, pressure, energy, and beginning condition must all be taken into account. We may measure the same parameters to determine the system's ultimate state once the time period during which we are watching it has passed.
Energy transfer, which results in work done on the system or by the system, often governs these changes.
Increasing the pressure of a gas in a container while the temperature is constant is an illustration of a thermodynamic process.
Any thermodynamic system's state may be expressed using a wide range of characteristics, including temperature, pressure, volume, and internal energy. If two out of the three parameters are fixed, the value of any one of these parameters may be determined. We may achieve this by applying the formula PV = RT.
Isothermal Process
The process in which the system's temperature stays constant is known as the isothermal process. There is some heat transmission, but it usually happens very slowly, allowing the system to reach thermal equilibrium.
Since, W = ∫PdV
From Gas Law,
PV = nRT
P = nRT/V
Putting the value of P, we get:
W = nRT ln VB/VA
If VB > VA, the work done will be positive.
If VB < VA, the work done is negative.
Internal energy is constant in such systems because the temperature is constant, ΔU = 0. Therefore, according to the first law of thermodynamics,
Q = ΔU + W
Therefore, Q = W.
Cyclic Process
A cycle is a thermodynamic process in which a system undergoes periodic changes to all of its attributes, which eventually return to their starting states with no overall change in the system's internal energy.
Thermodynamics in physics is a branch that deals with heat, work and temperature, and their relation to energy, radiation and physical properties of matter.
Important Terms
System
A thermodynamic system is a specific portion of matter with a definite boundary on which our attention is focused. The system boundary may be real or imaginary, fixed or deformable.
There are three types of systems:
Isolated System – An isolated system cannot exchange both energy and mass with its surroundings. The universe is considered an isolated system.
Closed System – Across the boundary of the closed system, the transfer of energy takes place but the transfer of mass doesn’t take place. Refrigerators and compression of gas in the piston-cylinder assembly are examples of closed systems.
Open System – In an open system, the mass and energy both may be transferred between the system and surroundings. A steam turbine is an example of an open system.
Thermodynamic Process
A system undergoes a thermodynamic process when there is some energetic change within the system that is associated with changes in pressure, volume and internal energy.
There are four types of thermodynamic process that have their unique properties, and they are:
Adiabatic Process – A process in which no heat transfer takes place.
Isochoric Process – A thermodynamic process taking place at constant volume is known as the isochoric process.
Isobaric Process – A process in which no change in pressure occurs.
Isothermal Process – A process in which no change in temperature occurs.
Laws of Thermodynamics
Zeroth Law of Thermodynamics
The Zeroth law of thermodynamics states that if two bodies are individually in equilibrium with a separate third body, then the first two bodies are also in thermal equilibrium with each other.
First Law of Thermodynamics
The First law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic processes, distinguishing three kinds of transfer of energy, as heat, as thermodynamic work, and as energy associated with matter transfer, and relating them to a function of a body's state, called internal energy.
Third law of thermodynamics states, regarding the properties of closed systems in thermodynamic equilibrium: The entropy of a system approaches a constant value when its temperature approaches absolute zero.
