Limitations of First Law of Thermodynamics
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the First Law of Thermodynamics state?

  • The direction of energy transfer is always from higher to lower temperature.
  • Energy can be created or destroyed.
  • Energy is conserved, but the direction of energy transfer is not specified. (correct)
  • Only heat energy can be transferred, not work.

    • What is a limitation of the First Law of Thermodynamics?

  • It specifies the direction of energy transfer.
  • It only applies to closed systems.
  • It only applies to open systems.
  • It does not specify the direction of energy transfer. (correct)

    • What happens when an ice cream is left open to the atmosphere?

  • It solidifies without doing any work.
  • It absorbs heat and gets melted. (correct)
  • It becomes colder than the atmosphere.
  • It remains unchanged.

    • In Joule's experiment, what happens to the temperature of the water?

    <p>It increases due to the work transforming into heat.</p> Signup and view all the answers

    What happens to the brakes of a stopped vehicle?

    <p>Their internal energy increases due to the decrease in kinetic energy.</p> Signup and view all the answers

    What is the purpose of studying the second law of thermodynamics?

    <p>To understand the limitations of the first law of thermodynamics</p> Signup and view all the answers

    What is a thermal reservoir?

    <p>A large system with a high thermal energy capacity</p> Signup and view all the answers

    What is the efficiency of a heat engine?

    <p>The ratio of output work to input heat</p> Signup and view all the answers

    What is the Coefficient of Performance (COP) of a refrigerator?

    <p>The ratio of heat removed from the cold reservoir to the work done</p> Signup and view all the answers

    What is the relation between the COP of a heat pump and the efficiency of a heat engine?

    <p>They are reciprocal</p> Signup and view all the answers

    What is a characteristic of a reversible process?

    <p>It is internally and externally reversible.</p> Signup and view all the answers

    What is the main difference between a reversible and irreversible process?

    <p>The presence of friction.</p> Signup and view all the answers

    What is the purpose of the cylinder head in a Carnot cycle?

    <p>To act as a perfect heat conductor or insulator.</p> Signup and view all the answers

    What is the result of heat transfer during an irreversible process?

    <p>Heat is generated and transferred to the surroundings.</p> Signup and view all the answers

    What is the name of the machine that converts internal energy from the atmosphere into work with 100% efficiency?

    <p>PMM-II</p> Signup and view all the answers

    What is the definition of thermal efficiency of a Carnot engine?

    <p>The ratio of work output to heat input</p> Signup and view all the answers

    What is the expression for the efficiency of a Carnot engine?

    <p>1 - (T_c / T_h)</p> Signup and view all the answers

    Why is a Carnot cycle not practical for real-world engines?

    <p>Because it is not possible to perform a frictionless process and the piston needs to move slowly for isothermal process</p> Signup and view all the answers

    What is the significance of the Carnot theorem?

    <p>It states that no heat engine can have a higher efficiency than a reversible engine</p> Signup and view all the answers

    What is the temperature of the triple point of water in Kelvin?

    <p>273.16 K</p> Signup and view all the answers

    What is the characteristic of the absolute thermodynamic temperature scale?

    <p>It is a function of temperature only</p> Signup and view all the answers

    What is the characteristic of the thermodynamic temperature scale?

    <p>It is a linear scale.</p> Signup and view all the answers

    What is the purpose of the reverse Carnot cycle?

    <p>To transfer heat from a colder body to a hotter body.</p> Signup and view all the answers

    What is the inequality of Clausius?

    <p>(dQ/T) = 0</p> Signup and view all the answers

    What is entropy typically measured in?

    <p>Joules per Kelvin (J/K)</p> Signup and view all the answers

    What is the significance of entropy being a state function?

    <p>It means that only changes in entropy are important.</p> Signup and view all the answers

    What is the relationship between entropy and the number of possible microstates in a system?

    <p>Higher entropy corresponds to a larger number of possible microstates.</p> Signup and view all the answers

    What happens to the total entropy of an isolated system over time?

    <p>It always increases.</p> Signup and view all the answers

    What is the significance of the principle of increase of entropy?

    <p>It implies that energy becomes less available to do work.</p> Signup and view all the answers

    What is a characteristic of a reversible process?

    <p>Entropy remains constant.</p> Signup and view all the answers

    What is the relationship between entropy and the amount of energy unavailable to do work?

    <p>Higher entropy corresponds to less energy available to do work.</p> Signup and view all the answers

    Why is it impossible to restore the initial state of an isolated system?

    <p>Because entropy always increases.</p> Signup and view all the answers

    What is the significance of the second law of thermodynamics?

    <p>It implies that entropy always increases in a closed system.</p> Signup and view all the answers

    What happens to the disorder and randomness of a system over time?

    <p>They always increase.</p> Signup and view all the answers

    What is the implication of the second law of thermodynamics on the behavior of energy and matter?

    <p>It implies that energy becomes less available to do work over time.</p> Signup and view all the answers

    What is the sole effect of an engine working in a cyclic process according to Kelvin-Plank statement?

    <p>To convert only part of the heat supplied to it into an equivalent amount of work</p> Signup and view all the answers

    What is the violation of Kelvin-Plank statement equivalent to?

    <p>Violation of Clausius statement</p> Signup and view all the answers

    What is a Perpetual Motion Machine of the second kind (P.M.M.-II)?

    <p>A machine that converts all the internal energy into useful work with 100% efficiency</p> Signup and view all the answers

    What is the purpose of a reversible process?

    <p>To determine the maximum possible efficiency of a heat engine</p> Signup and view all the answers

    Which of the following is a characteristic of a Perpetual Motion Machine of the first kind (P.M.M.-I)?

    <p>It gives continuous work without receiving energy from other systems</p> Signup and view all the answers

    Study Notes

    Limitation of First Law of Thermodynamics

    • First law of thermodynamics states that energy is conserved, but it does not specify the direction of energy transfer.
    • The first law is necessary but not sufficient for a process to occur.
    • Examples of the limitation of the first law:
      • Ice cream melting when left open to the atmosphere, but it does not solidify back without external work.
      • Joule's experiment, where the fall of weight causes rotation of paddle and increases temperature of water, but increase in temperature of water does not lift the weight.
      • A running vehicle stopping due to brakes, where the internal energy of brakes increases, but the hot brakes do not cause the wheels to rotate.

    Basic Definitions

    • Thermal reservoir: a large system that can absorb or release energy as heat without changing its temperature.
    • Heat engine: a cyclically operating device that absorbs energy as heat from a high-temperature reservoir, converts part of it into work, and rejects the rest to a low-temperature reservoir.
    • Efficiency of a heat engine: ratio of work output to heat supply.
    • Heat pump: a device that transfers heat energy from a cold body to a hot body, using a small amount of external work.

    Second Law of Thermodynamics

    • Kelvin-Planck statement: it is impossible to construct an engine that converts all the heat energy into work.
    • Clausius statement: it is impossible to construct a heat pump that transfers heat from a cold body to a hot body without external work.
    • Both statements are equivalent and imply that it is impossible to have a machine that violates the second law of thermodynamics.

    Perpetual Motion Machines (PMM)

    • PMM-I: a machine that violates the first law of thermodynamics, producing work without energy input.
    • PMM-II: a machine that violates the second law of thermodynamics, converting internal energy into work with 100% efficiency.
    • Both types of PMM are impossible.

    Concept of Reversibility and Irreversibility

    • Reversible process: a process that can be reversed without changing the system or surroundings.
    • Irreversible process: a process that cannot be reversed, resulting in a change in the system or surroundings.
    • Causes of irreversibility: friction, heat transfer, and other factors.

    Carnot Cycle

    • A reversible cycle that consists of four processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.
    • The Carnot cycle is the most efficient cycle possible, with an efficiency of 1 - (T_c / T_h), where T_c and T_h are the temperatures of the cold and hot reservoirs, respectively.

    Carnot Theorem

    • All heat engines operating between a given temperature source and sink have an efficiency less than or equal to the Carnot engine.
    • The Carnot theorem is a fundamental limit on the efficiency of heat engines.

    Absolute Thermodynamic Temperature Scale

    • A temperature scale based on the principles of thermodynamics, with the triple point of water defined as 273.16 K and absolute zero defined as 0 K.
    • The absolute temperature scale is a universal scale that is applicable to all systems, regardless of their composition or state.

    Reverse Carnot Cycle (Carnot Refrigeration Cycle)

    • A cycle that operates in reverse, transferring heat from a cold body to a hot body using external work.### The Carnot Cycle
    • The Carnot cycle is a thermodynamic cycle that uses a refrigerant to transfer heat from a colder body to a hotter body.
    • The cycle consists of four stages: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.
    • The reverse Carnot cycle is the basis for most refrigeration systems, including household refrigerators and freezers, industrial chillers, and cryogenic coolers.

    The Inequality of Clausius

    • The inequality of Clausius states that (dQ/T) = 0, where dQ is the amount of heat transferred and T is the temperature at which the heat transfer occurs.
    • The inequality indicates that in a reversible process, the integral is equal to zero (S = Q/T), while in an irreversible process, the integral is less than zero (S > Q/T).
    • The inequality is a statement of the second law of thermodynamics, which dictates that the total entropy of an isolated system will always increase over time.

    Entropy

    • Entropy is a measure of the amount of disorder, randomness, or uncertainty in a system.
    • Entropy can be thought of as a measure of the amount of energy in a system that is unavailable to do work.
    • Entropy is typically denoted by the symbol "S" and is measured in units of joules per kelvin (J/K).
    • Entropy is a state function, meaning that only the change in entropy (S) is important, not the absolute value.
    • Entropy can be related to the number of possible microstates in a system, with higher entropy corresponding to a larger number of possible microstates.

    Principle of Increase of Entropy

    • The principle of increase of entropy states that the total entropy of an isolated system will always increase over time, except in reversible processes.
    • Entropy always increases over time in a closed system, remains constant in a reversible process, and never decreases spontaneously in an isolated system.
    • The principle has far-reaching implications, including energy degradation, disorder and randomness, and irreversibility.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Explore the limitations of the first law of thermodynamics, including its inability to specify the direction of energy transfer and its insufficiency for a process to occur.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser