Zeroth Law of Thermodynamics , First Law of Thermodynamics, Second Law of Thermodynamics

1. Ms.Viddya S. Patil
Assistant Professor
Department of Mechanical Engineering
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Sharad Institute of Technology, College of
Engineering, Yadrav- Ichalkarnji
Department of Mechanical Engineering
Lecture 2:
Introduction to Thermal Engineering
Fundamentals of Mechanical
Engineering

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Content
1. Zeroth Law of Thermodynamics
2. first law of thermodynamics and its applications
3. Limitations of first of thermodynamics
4. Second law of thermodynamics and its applications

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1. Zeroth Law of Thermodynamics
The zeroth law of thermodynamics is a fundamental principle that is essential for understanding heat and
temperature. It is used in a wide variety of applications, from cooking and refrigeration to the design of
engines and power plants.
The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third
system, then they are in thermal equilibrium with each other. In simpler terms, it means that if two objects
are at the same temperature as a third object, then they are at the same temperature as each other.

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Here are some examples of the zeroth law in action:
1. If you put a cup of hot coffee in a bowl of cold water, the coffee will eventually cool
down and the water will heat up until they are both at the same temperature.
2. If you put two ice cubes in a glass of warm water, the ice cubes will melt and the water
will cool down until they are both at the same temperature.
3. If you touch a hot stove, your hand will get burned because heat will flow from the stove
to your hand.

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2. First law of thermodynamics
The First Law of Thermodynamics is a statement of energy conservation, which states that energy
cannot be created or destroyed, only converted from one form to another. This law is also known as
the law of energy conservation or the principle of energy conservation. It is a fundamental law of
physics that applies to all physical systems, including thermodynamic systems. The first law of
thermodynamics can be used to predict a thermodynamic system’s behavior and determine the
changes in energy that occur during various processes. It is an important law used to understand
systems’ behavior and design new energy technologies and devices.
This equation can be written as:
ΔU = Q – W

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Applications-
1. Automobile Engine
2. Human Metabolism
3. Refrigeration
4. Electric Power Plant
5. Solar Panels
6. Battery Charging
7. Hydraulic System
8. Wind Turbines
9. Food Cooking
10. Nuclear Reactors
Source of Image: https://studiousguy.com/first-law-of-thermodynamics-examples/

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Limitations of the First Law of Thermodynamics are:
1. The first law of thermodynamics fails to give the feasibility of the process or change of state that
the system undergoes.
2. It fails to explain the direction of heat flow.
3. It doesn't say the process is a spontaneous or non-spontaneous process.
Source of Image:https://lawofthermodynamicsinfo.com/limitations-of-first-law-of-thermodynamics/

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Second law of thermodynamics
There are two statements on the second law of thermodynamics, and they are
1. Kelvin- Planck Statement
2. Clausius Statement
Kelvin-Planck Statement
“It is impossible to construct a device which operates on a cycle and produces no other effect than the transfer of
heat from a single body to produce work.” This means that it is impossible to construct an engine whose sole
purpose is to convert the heat from a high-temperature source/reservoir into an equal amount of work.

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Clausius’s Statement
It is impossible to construct a device operating in a cycle that
can transfer heat from a colder body to a warmer one without
consuming any work. Also, energy will not flow spontaneously
from a low-temperature object to a higher-temperature object. It
is important to note that we are referring to the net transfer of
energy. Energy transfer can take place from a cold object to a
hot object by the transfer of energetic particles or
electromagnetic radiation. However, the net transfer will occur
from the hot object to the cold object in any spontaneous
process. And some form of work is needed to transfer the net
energy to the hot object. In other words, unless the compressor
is driven by an external source, the refrigerator won’t be able to
operate. The heat pump and refrigerator work on Clausius’s
statement.
Both Clausius’s and Kelvin’s statements are equivalent, i.e., a
device violating Clausius’s statement will also violate Kelvin’s
statement and vice versa.
Source of Image: https://www.nuclear-
power.com/nuclear-engineering/thermodynamics/laws-
of-thermodynamics/second-law-of-
thermodynamics/clausius-statement-of-the-second-law/

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Applications of the Second Law
1. Refrigeration: Transferring heat from a cold reservoir to a hot one (requires work
input).
2. Heat Engines: Converting heat into useful work (limited by Carnot efficiency).
3. Material Science: Predicting material stability and phase transitions.

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This video is prepared for academic use only.