12:23 AM
M V Rao
Basic Concept And First Law
1. What do you understand by pure substance?
A pure substance is defined as one that is homogeneous and invariable in chemical composition throughout its mass.
2. Define thermodynamic system.
A thermodynamic system is defined as a quantity of matter or a region in space, on which attention in the analysis of the problem is concentrated.
3. Name the different types of system.
1. Closed system (only energy transfer and no mass transfer)
2. Open system (Both energy and mass transfer)
3. Isolated system (No mass and energy transfer)
4. Define thermodynamic equilibrium.
If a system is in Mechanical, Thermal and Chemical Equilibrium then the system is in thermodynamically equilibrium.
(or)
If the system is isolated from its surrounding there will be no change in the macroscopic property, then the system is said to exist in a state of thermodynamic equilibrium.
5. What do you mean by quasi-static process?
Equilibrium state or Quasi-static process:
Infinite slowness is the characteristic feature of a quasi-static process. A quasi-static process is that a succession of equilibrium states. A quasi-static process is also called as reversible process.
6. Define Path function.
The work done by a process does not depend upon the end of the process. It depends on the path of the system follows from state 1 to state 2. Hence work is called a path function.
7. Define point function.
Thermodynamic properties are point functions. The change in a thermodynamic property of a system is a change of state is independent of the path and depends only on the initial and final states of the system.
8. Name and explain the two types of properties.
The two types of properties are intensive property and extensive property.
Intensive Property: It is independent of the mass of the system.
Example: Pressure, temperature, specific volume, specific energy, density.
Extensive Property: It is dependent on the mass of the system.
Example: Volume, energy. If the mass is increased the values of the extensive properties also increase.
9. Explain homogeneous and heterogeneous system.
The system consist of single phase is called homogeneous system and the system consist of more than one phase is called heterogeneous system.
10. What is a steady flow process?
Steady flow means that the rates of flow of mass and energy across the control surface are constant.
11. Prove that for an isolated system, there is no change in internal energy.
In isolated system there is no interaction between the system and the surroundings. There is no mass transfer and energy transfer. According to first law of thermodynamics as dQ = dU + dW; dU = dQ – dW; dQ = 0, dW = 0,
Therefore dU = 0 by integrating the above equation U = constant, therefore the internal energy is constant for isolated system.
12. Indicate the practical application of steady flow energy equation.
1. Turbine
2. Nozzle
3. Condenser
4. Compressor
13. Define system.
It is defined as the quantity of the matter or a region in space upon which we focus attention to study its property.
14. Define cycle.
It is defined as a series of state changes such that the final state is identical with the initial state.
16. Explain Mechanical equilibrium.
If the forces are balanced between the system and surroundings are called Mechanical equilibrium
17. Explain Chemical equilibrium.
If there is no chemical reaction or transfer of matter form one part of the system to another is called Chemical equilibrium
18. Explain Thermal equilibrium.
If the temperature difference between the system and surroundings is zero then it is in Thermal equilibrium.
19. Define Zeroth law of Thermodynamics.
When two systems are separately in thermal equilibrium with a third system then they themselves are in thermal equilibrium with each other.
20. What are the limitations of first law of thermodynamics?
1. According to first law of thermodynamics heat and work are mutually convertible during any cycle of a closed system. But this law does not specify the possible conditions under which the heat is converted into work.
2. According to the first law of thermodynamics it is impossible to transfer heat from lower temperature to higher temperature.
3. It does not give any information regarding change of state or whether the process is possible or not.
4. The law does not specify the direction of heat and work.
21. What is perpetual motion machine of first kind?
It is defined as a machine, which produces work energy without consuming an equivalent of energy from other source. It is impossible to obtain in actual practice, because no machine can produce energy of its own without consuming any other form of energy.
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