We know from the second law of thermodynamics that a heat engine cannot be 100 percent efficient, since there must always be some heat transfer Qc to the environment.
What sets the limits on efficiency of a heat engine?
The temperature of the cold reservoir sets the limit on the efficiency of a heat engine.
On what factors does the efficiency of heat engine depends?
The efficiency of an ideal heat engine only depends on the temperature of source and sink.
How can we determine the maximum possible efficiency of a heat engine?
Since temperatures are given for the hot and cold reservoirs of this heat engine, EffC=1−TcTh E f f C = 1 − T c T h can be used to calculate the Carnot (maximum theoretical) efficiency. Those temperatures must first be converted to kelvins.
What are the limitations of first law of thermodynamics justify the need of second law?
The limitation of the first law of thermodynamics is that it does not say anything about the direction of flow of heat. It does not say anything whether the process is a spontaneous process or not. The reverse process is not possible. In actual practice, the heat doesn’t convert completely into work.
How does the second law of thermodynamics apply to heat engines?
The Second Law of Thermodynamics (first expression)
Heat transfer occurs spontaneously from higher- to lower-temperature bodies but never spontaneously in the reverse direction. Another way of stating this: It is impossible for any process to have as its sole result heat transfer from a cooler to a hotter object.
What is the minimum efficiency of a heat engine?
Step by step solution by experts to help you in doubt clearance & scoring excellent marks in exams. temperature difference of source and sink is minimum. temperature difference of source and sink is maximum.
Why are heat engines inefficient in general?
Why are heat engines inefficient, in general? a. Temperatures are so high that a great deal of heat is lost to the environment. … Heat engines attempt to convert the worst source of energy into the best.
What is the most efficient heat engine?
The most efficient heat engine cycle is the Carnot cycle, consisting of two isothermal processes and two adiabatic processes. The Carnot cycle can be thought of as the most efficient heat engine cycle allowed by physical laws.
How can you increase the efficiency of a heat engine?
Therefore, the efficiency of the heat engine can be increased by decreasing the temperature of the cold sink or increasing the temperature of the hot source.
Is Carnot engine 100 efficient?
In order to achieve 100% efficiency (η=1), Q2 must be equal to 0 which means that all the heat form the source is converted to work. The temperature of sink means a negative temperature on the absolute scale at which the temperature is greater than unity.
What is a perfect heat engine?
enrgy associated with a single degree of freedom connected with an external parameter. of some outside device. Typically the engine goes through a cycle, returning to its initial. state after having turned some heat into work. Think about the gasoline engine in your.
What is the second law of thermodynamics called?
The second law of thermodynamics establishes the concept of entropy as a physical property of a thermodynamic system. … If all processes in the system are reversible, the entropy is constant.
What are the limitations of Second Law of Thermodynamics?
There are no limitations to the second law of thermodynamics. However, there is a misconception that the second law is only applicable to the closed system.
What is second law of thermodynamics in physics?
the second law of thermodynamics: A law stating that states that the entropy of an isolated system never decreases, because isolated systems spontaneously evolve toward thermodynamic equilibrium—the state of maximum entropy. Equivalently, perpetual motion machines of the second kind are impossible.
What violates the First and Second Law of Thermodynamics?
A device that violates the First law of thermodynamics (by creating energy) is called a Perpetual Motion Machine of the first kind. A device that violates the Second law of thermodynamics is called a Perpetual Motion Machine of the Second kind. … So this is a system creating energy and therefore violating the first law.