Thermodynamics is the branch of Physics that deals with heat and other forms of energy. In particular, thermodynamics explains how thermal energy gets converted to and from other forms of energy, and its effect on matter.
Thermodynamics Process
A thermodynamic process involves the transfer of energy within a system or between systems. It involves properties like pressure, temperature and volume. The present values of the properties of a system are called the thermodynamic state of the system. An example of a thermodynamic process is food staying cold inside a refrigerator. In a refrigerator, the heat is pulled out of the inner compartments and transferred to the outside air.
Types of Thermodynamic Process
Isobaric Process: Pressure remains constant in an isobaric process. Let us take the example of a piston and cylinder arrangement to explain the process. The pressure of the gases inside the cylinder increases when fuel burns. The pressure inside the cylinder can be kept constant by allowing the piston to move upwards.
Isothermal Process: A process in which the temperature remains constant is called the isothermal process. This means that the internal energy of the system will be constant since the temperature is the measure of the kinetic energy of the molecules.
Adiabatic Process: It is a process in which there is no heat transfer between the system and its surroundings. However, the temperature changes due to internal system variation.
Isochoric Process: It is the process in which the volume remains constant.
Polytropic Process
Polytropic is a thermodynamic process that obeys the relation
PVx = C.
Here, P is the Pressure
V is the Volume
x is the Polytropic Index
C is the Constant
The polytropic index will take any value between 0 and ∞, depending on the process.
| Value of x (PVx = C) | Process |
| x = 0 | Isobaric (dP = 0) |
| x = 1 | Isothermal (dT = 0) |
| x = n | Polytropic |
| x = γ | Adiabatic (δQ = 0) |
| x = ∞ | Isochoric (dV = 0) |
Graphical Comparison of Thermodynamic Process
The changes in pressure with respect to the volume are given by the pressure-volume diagram or the PV diagram. The efficiency of the system can be determined using the PV diagram. The area under the curve of the PV diagram gives the work done to, or by, the system.
From the PV diagram for expansion, it is clear that for the same volume of expansion, the area under the isothermal curve is more than the adiabatic curve. Therefore, the isothermal work is more than the adiabatic work. The work done due to expansion is calculated by adding a positive sign.
From the compression curve, it can be seen that the area under the adiabatic curve is more than the isothermal curve. In the case of compression, the work done is calculated by adding a negative sign. Therefore, even in compression, isothermal work will be more than adiabatic work.
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Frequently Asked Questions on Escape Velocity
Define escape velocity.
The minimum speed required to project a body vertically upward from the earth’s surface so that it never returns to the earth’s surface is called escape speed or escape velocity.
Write the expression for escape velocity.
ve = √2GM/R =√2gR
R is the radius of the earth.
g is the acceleration due to gravity.
What is the value of escape velocity on the surface of the earth?
The value is 11.2 km/s.
What is the relation between escape velocity and orbital velocity?
ve = √2v0
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