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A foundational understanding of engineering thermodynamics, covering key concepts such as thermodynamic systems, properties, equilibrium, and processes. it presents a series of questions and answers that test comprehension of these fundamental principles, making it a valuable resource for students studying thermodynamics. The questions delve into the definitions of thermodynamic systems, their classifications, and the distinctions between various types of processes and properties. This resource is particularly useful for self-assessment and exam preparation.
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BIBIN.C
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
RMK COLLEGE OF ENGINEERING AND TECHNOLOGY
GUMMIDIPOONDI TALUK
TIRUVALLUR DIST
1. What is meant by Thermodynamics? Thermodynamics is the science of energy transfer and its effects on physical properties of substances. 2. Define the term thermal engineering. Thermal engineering is the science that deals with the energy transfer to practical applications such as energy transfer power generation, refrigeration, gas compression and its effect on the properties of working substance. 3. What is meant by Macroscopic approach in thermodynamics? Macroscopic thermodynamics deals with the effects of the action of many molecules concerned. 4. What is Microscopic (or) Statistical thermodynamics? Microscopic approach in thermodynamics deals with the study of the behaviour of the system by summing up the behaviour of each molecule 5. The two approaches by which the behaviour of matter can be studied in thermodynamics are ................. and ........................ [Ans: Macroscopic, Microscopic] 6. Give few applications of thermodynamic laws and principles: The laws and principles are applied in the steam and nuclear power plants, IC engines, Gas turbines, refrigeration etc. 7. What is thermodynamic medium? A matter of growing material chosen for the conversion of one form of energy into another is called thermodynamic medium.
13. Differentiate closed and open system.
Closed System Open System
19. In an isolated system, the total energy of the system............................ Ans: remains constant. 20. What is meant by control volume? Control volume is an imaginary region within which interactions are studied. 21. What is known as control surface? The boundary of the control volume is called as control surface. 22. Define change of state of a system Any process in which one or more of the properties of the system changes is called change of state. 23. What is meant by thermodynamic property? Thermodynamic property is any characteristic of a substance which is used to identify the state of the system and can be measured, when the system remains in an equilibrium state. 24. How do you classify the property? Thermodynamic property can be classified into two types. i. Intensive or Intrinsic property ii. Extensive and Extrinsic property 25. What is meant by intensive or intrinsic property? Give an example. The properties which are independent on the mass of the system is called intensive properties. Example: Pressure, Temperature, Specific Volume etc.
30. What are the conditions for thermodynamic equilibrium? The system in thermodynamic equilibrium must essentially be in i. Mechanical Equilibrium ii. Thermal equilibrium iii. Chemical equilibrium 31. What is meant by thermodynamic equilibrium? When a system is in thermodynamic equilibrium, it should satisfy the following three conditions. i. Mechanical Equilibrium: - Pressure remains constant ii. Thermal equilibrium: - Temperature remains constant iii. Chemical equilibrium: There is no chemical reaction. 32. Explain Mechanical equilibrium. If the forces are balanced between the system and surroundings are called Mechanical equilibrium 33. 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 34. Explain Thermal equilibrium. If the temperature difference between the system and surroundings is zero then it is in Thermal equilibrium. 35. Define nuclear equilibrium A system is said to be in nuclear equilibrium when nuclear reactions such as fusion, fission reaction does not cause any change.
36. Define magnetic equilibrium A system is said to be in magnetic equilibrium when the magnetisation and demagnetisation effects do not change its properties 37. when there is uniform pressure at all points of the system, then it is said to be in ......... Ans: Mechanical equilibrium 38. When a system wiII be in a state of thermodynamic equilibrium? A system is said to exist in a state of thermodynamic equilibrium, when no change in any microscopic property is registered, if the system is isolated from the surroundings. 39. Define continuum The Atomie structure of a substance is disregarded in classical thermodynamics and the substance is viewed to be a continuous, homogenous matter without microscopic holes. This concept is called as continuum. 40. Define the term process It is defined as the change of state undergone by a gas due to energy flow. 41. Define the term thermodynamic Cycle When a system undergoes a series of processes and return to its initial condition, it is known as thermodynamic cycle. 42. What is meant by open cycle? In an open cycle, the same working substance will be exhausted to the surroundings after expansion. 43. What is meant by closed cycle? In a closed cycle, the same working substance will recalculates again and again.
49. What is meant by Path function? The quantities which are dependent on the process or path followed by the system is known as path functions. Example: Heat transfer, work transfer. 50. Define absolute pressure The total algebric sum of the atmospherie pressure and gauge pressure is called absolute pressure. 51. What is gauge pressure? The pressure measured above the atmospherie pressure gauge pressure. 52. Define atmospheric pressure Pressure exerted by air on a column of 760 mm of mercury is called atmospherie pressure. 53. What is meant by state of a system? State is an unique condition of the system and at equilibrium. It can be identified by its properties, such as pressure, volume. 54. Define path of change of state The succession equilibrium states passed through, is called the path of change of state. 55. Define energy Energy of system is the ability or capacity to do work. 56. Define stored energy Energy possessed by a system within its boundaries is called stored energy. Example: Potential energy.
57. Define power The rate of energy transfer is called power. 58. Define transit energy Energy possessed by a system which is capable of crossing its boundaries is.caIled transit energy. Example: Heat energy, Electrical energy'. 59. Define internal energy Energy possessed by a substance due to its molecular arrangement and. motion of its molecules is called internal energy. 60. What is meant by thermodynamic work? A thermodynamic work is said to be do ne by a system if its sole effect outside its boundary is equivalent to raising a weight against the force of gravity. 61. What is meant by thermodynamic work? It is the work done by the system when the energy transferred across the boundary of the system. It is mainly due to intensive property difference between the system and surroundings.
62.What is the work done in a closed system in terms pressure and volume? Workdone = Pdv.
63. Work done by a system is............. Ans: Positive. 64. Work done on a system is ............... Ans: Negative 65. Heat supplied to the system is...................... Ans: Positive.
75. State the law of conservation of energy Energy can neither be created nor destroyed, but it can be transferred from one form to another. 76. State the First law of thermodynamics First law of thermodynamics states that when system undergoes a cyclic process the net heat transfer is equal to work transfer. 77. What are the limitations of first law of thermodynamics? a. 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. b. According to the first law of thermodynamics it is impossible to transfer heat from lower temperature to higher temperature. c. It does not give any information regarding change of state or whether the process is possible or not. d. The law does not specify the direction of heat and work. 78. Define the term enthalpy? The Combination of internal energy and flow energy is known as enthalpy of the system. It may also be defined as the total heat of the substance.
Mathematically,
Enthalpy (H) = U + p v ……..KJ Where, U – internal energy p – Pressure v – Volume In terms of Cp & T → H = m Cp (T 2 -T 1 ) ……… KJ
79. Give the general gas energy equations. dH = dE + dW. 80. Define the term internal energy Internal energy of a gas is the energy stored in a gas due to its molecular interactions. It is also defined as the energy possessed by a gas at a given temperature. 81. Define Heat. Heat is the energy crossing the boundary due to the temperature difference between the system and surroundings. 82. Define Specific heat capacity at constant pressure. It is defined as the amount of heat energy required to raise or lower the temperature of unit mass of the substance through one degree when the pressure kept constant. It is denoted by CP. 83. Define Specific heat capacity at constant volume. It is defined as the amount of heat energy required to raise or lower the temperature of unit mass of the substance through one degree when volume kept constant. It is denoted by CV. 84. 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. 85. Define entropy of a pure substance. Entropy is an important thermodynamic property, which increases with addition of heat and decreases with its removal. Entropy is a function of temperature only. It is an unavailability of energy during energy transfer.
92. Write down the characteristic gas equation. Characteristic gas equation is pV = mRT Where, p = pressure V = Volume R = Characteristic gas constant T = Temperature. 93. What is meant by steady flow process? During the process the rate of flow of mass and energy across the boundary remains constant, is known as steady flow process. OR Steady flow means that the rates of flow of mass and energy across the control surface are constant. 94. What is the difference between steady flow and non – flow process? During the steady flow process the rate of flow of mass and energy across the boundary remains constant.
In case of non – flow across the system and boundary.
95. Indicate the practical application of steady flow energy equation. i. Turbine ii. Nozzle iii. Condenser iv. Compressor v. Pump 96. Work done in a free expansion process is _________ Ans: Zero
97. Explain entropy. It is an important thermodynamic property of the substance. It is the measure of molecular disorder. It is denoted by S. The measurement of change in entropy for reversible process is obtained by the quantity of heat received or rejected to absolute temperature. 98. What are the important characteristics of entropy? i. If the heat is supplied to the system then the entropy will increase. ii. If the heat is rejected to the system then the entropy will decrease. iii. The entropy is constant for all adiabatic frictionless process. iv. The entropy increases if temperature of heat is lowered without work being done as in throttling process. v. If the entropy is maximum, then there is a minimum availability for conversion in to work. vi. If the entropy is minimum then there is a maximum availability for conversion into work. 99. 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. 100. Which property is constant during throttling? Enthalpy
1. State the Kelvin – Plank statement of second law of thermodynamics Kelvin – Plank states that it is impossible to construct a heat engine working on cyclic process, whose only purpose is to convert all the heat energy given to it into an equal amount of work. OR It is impossible to construct a heat engine to produce network in a complete cycle if it exchanges heat from a single reservoir at single fixed temperature. 2. State Clausius statement of second law of thermodynamics.
It states that heat can flow from hot body to cold without any external aid but heat cannot flow from cold body to hot body without any external aid. OR It is impossible for a self-acting machine working in a cyclic process, to transfer heat from a body at lower temperature to a body at a higher temperature without the aid of an external agency.
3. State Carnot theorem. It states that no heat engine operating in a cycle between two constant temperature heat reservoirs can be more efficient than a reversible engine operating between the same reservoirs. 4. What is absolute entropy(Third law of Thermodynamics)? The entropy measured for all perfect crystalline solids at absolute zero temperature is known as absolute entropy. 5. What are the Corollaries of Carnot theorem?
i. In all reversible engine operating between the two given thermal reservoirs with fixed temperature, have the same efficiency. ii. The efficiency of any reversible heat engine operating between two reservoirs is independent of the nature of the working fluid and depends only on the temperature of the reservoirs.
6. Define Heat pump. A heat pump is a device, which is working in a cycle and transfers heat from lower temperature to higher temperature. 7. Define Heat engine. Heat engine is a machine, which is used to convert the heat energy into mechanical work in a cyclic process. OR A heat engine is a device which is used to convert the thermal energy into mechanical energy. 8. What are the assumptions made on heat engine? i. The source and sink are maintained at constant temperature. ii. The source and sink has infinite heat capacity. 9. What is the difference between a heat pump and a refrigerator? Heat pump is a device which operating in cyclic process, maintains the temperature of a hot body at a temperature higher than the temperature of surroundings.
A refrigerator is a device which operating in a cyclic process, maintains the temperature of a cold body at a temperature lower than the temperature of the surroundings.
10. Define the term COP?
