Undergraduate
  1. Classical mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. projectile motion  1.1.4. Relative speed  1.1.5. Uniform circular motion  1.1.6. Non-uniform circular motion  1.1.7. Reference frames and transformations  1.2. Newton's Laws of Motion  1.2.1. First law of motion  1.2.2. Second law of motion  1.2.3. Third Law of Motion  1.2.4. Applications of Newton's Laws  1.2.5. Friction and its types  1.2.6. Free Body Diagram  1.2.7. Constraints and pseudo-forces  1.3. Work and Energy  1.3.1. work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy in classical mechanics  1.3.5. Conservative and non-conservative forces  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.4. Speed and collisions  1.4.1. Linear momentum  1.4.2. Conservation of momentum  1.4.3. Impulse and impact force  1.4.4. Elastic and inelastic collision  1.4.5. Center of mass and speed  1.4.6. Rocket Propulsion  1.5. Rotational motion  1.5.1. Torque and Angular Momentum  1.5.2. Moment of inertia  1.5.3. Rotational Kinematics  1.5.4. Rotational Energy  1.5.5. Rolling Motion  1.5.6. Precession and gyroscopic motion  1.6. Gravitational force  1.6.1. Newton's law of universal gravitation  1.6.2. Gravitational potential energy  1.6.3. Orbital mechanics  1.6.4. Kepler's laws of planetary motion  1.6.5. Gravitational field and potential  1.7. Fluid mechanics  1.7.1. Pressure and Pascal's Principle  1.7.2. Buoyancy and Archimedes' principle  1.7.3. Fluid Dynamics and Bernoulli's Principle  1.7.4. Viscosity and Poiseuille's law  1.7.5. Surface tension and capillarity  1.8. Oscillations and waves  1.8.1. Simple Harmonic Motion  1.8.2. Damped and driven oscillations  1.8.3. Coupled oscillations and common modes  1.8.4. Wave properties and types  1.8.5. Sound Waves and the Doppler Effect  1.8.6. Wave interference and superposition
  2. Electromagnetism  2.1. Electrostatics  2.1.1. Electric charge and properties  2.1.2. Coulomb's law  2.1.3. Electric field and electric potential  2.1.4. Gauss's Law  2.1.5. Capacitance and Dielectric  2.1.6. Electric dipole and potential energy  2.2. Electric circuits  2.2.1. Current and Resistance  2.2.2. Ohm's law  2.2.3. Kirchhoff's Laws  2.2.4. RC Circuit  2.2.5. AC Circuits and Reactance  2.2.6. Electric power and energy  2.3. Magnetism  2.3.1. Magnetic Fields and Forces  2.3.2. Ampere's Law  2.3.3. Magnetic dipole moment  2.3.4. Biot-Savart law  2.3.5. Magnetic Materials and Hysteresis  2.4. Electromagnetic induction  2.4.1. Faraday's Law  2.4.2. Lenz's law  2.4.3. Self and mutual induction  2.4.4. Transformers and Inductive Circuits  2.5. Maxwell's equations  2.5.1. Gauss's law for electricity  2.5.2. Gauss's law for magnetism  2.5.3. Faraday's law of induction  2.5.4. Ampere-Maxwell law  2.5.5. Electromagnetic waves
  3. Thermodynamics  3.1. Laws of Thermodynamics  3.1.1. Zeroth law of thermodynamics  3.1.2. First law of thermodynamics  3.1.3. Second Law  3.1.4. Third Law  3.2. Heat and work  3.2.1. Heat transfer (conduction, convection, radiation)  3.2.2. Thermal expansion  3.2.3. Heat engines and refrigerators  3.2.4. Carnot cycle and efficiency  3.3. Statistical mechanics  3.3.1. Maxwell–Boltzmann distribution  3.3.2. Entropy and Probability  3.3.3. Partition function  3.3.4. Fermi–Dirac and Bose–Einstein statistics
  4. Optics  4.1. Geometrical Optics  4.1.1. Reflection and Refraction  4.1.2. Mirrors and lenses  4.1.3. Optical Instruments  4.1.4. Fermat's principle  4.2. Wave optics  4.2.1. Interference in wave optics  4.2.2. Diffraction  4.2.3. Polarization  4.2.4. Coherence and holography
  5. Quantum mechanics  5.1. Wave–particle duality  5.1.1. Blackbody radiation in wave–particle duality in quantum mechanics  5.1.2. Photoelectric effect  5.1.3. Compton scattering  5.1.4. De Broglie wavelength  5.2. Schrödinger Equation  5.2.1. Time-independent Schrödinger equation  5.2.2. Particle in a box  5.2.3. Quantum Tunneling  5.2.4. Potential wells and obstacles  5.3. Quantum States  5.3.1. Wave function  5.3.2. Quantum operators  5.3.3. Heisenberg uncertainty principle  5.3.4. Angular momentum and spin
  6. Relativity  6.1. Special relativity  6.1.1. Lorentz transformations  6.1.2. Time expansion and length contraction  6.1.3. Relativistic energy and momentum  6.2. General relativity  6.2.1. Principle of Equivalence  6.2.2. Schwarzschild metric  6.2.3. Gravitational waves  6.2.4. Black holes and event horizons
  7. Solid state physics  7.1. Crystal structure  7.1.1. Bravais lattices  7.1.2. X-ray diffraction  7.1.3. Band theory  7.1.4. Phonons and lattice vibrations  7.2. Electrical and Magnetic Properties  7.2.1. Conductors, Semiconductors and Insulators  7.2.2. Superconductivity  7.2.3. Hall effect
  8. Nuclear and particle physics  8.1. Atomic Structure  8.1.1. Atomic Model  8.1.2. Nuclear binding energy  8.2. Radioactivity  8.2.1. Alpha, beta, gamma decay  8.2.2. Half life  8.2.3. Nuclear Fission and Fusion  8.3. Particle physics  8.3.1. Standard Model  8.3.2. Quarks and Leptons  8.3.3. antimatter  8.3.4. Fundamental interactions
  9. Astrophysics and cosmology  9.1. Stellar evolution  9.1.1. Star formation  9.1.2. Black holes and neutron stars  9.1.3. White dwarfs and supernovae  9.2. Cosmology  9.2.1. The Big Bang Theory  9.2.2. Dark matter and dark energy  9.2.3. Cosmic microwave background

Undergraduate ↓


Thermodynamics


Thermodynamics is an interesting branch of physics that deals with the study of heat, work, and energy. At its core, it explores how energy is transferred in physical processes and how it affects matter. This set of principles governs much of the natural world and technology. Thermodynamics lays the foundation for understanding how engines work, how refrigerators keep things cold, and even why our universe behaves the way it does on a large scale. Let's take a deeper dive into the fascinating world of thermodynamics.

Basic concepts

Before we get into the laws of thermodynamics, it is necessary to understand some basic concepts:

System and environment

In thermodynamics, we define the system as the part of the universe we are focusing on. Everything else outside of this system is its surroundings. For example, if you are studying a cup of coffee, the coffee is the system, and the air around it is the surroundings.

Types of systems

  • Open system: can exchange both energy and matter with its surroundings. An example of this is a pot of water placed on the stove without a lid.
  • Closed system: can exchange energy, but not matter, with its surroundings. An example of this is a sealed, hot water bottle, where only heat can pass through the walls.
  • Isolated system: cannot exchange energy or matter with its surroundings. An example of this is a perfect thermos bottle that keeps your drink hot without any heat loss or gain.

State variables

The properties that describe the state of a thermodynamic system are called state variables. Some of the key state variables include:

  • Temperature (T): A measure of the average kinetic energy of the particles in a substance.
  • Pressure (P): The force exerted per unit area by particles colliding with the walls of a container.
  • Volume (V): The amount of space occupied by the system.
  • Internal energy (U): The total energy contained in the system.

Processes and cycles

A thermodynamic process is a change that occurs in a system from one equilibrium state to another. There are different types of processes, including:

  • Isothermal: occurs at a constant temperature. Think of the slow expansion or contraction of a gas, where heat is exchanged to keep the temperature constant.
  • Adiabatic: Occurs without any heat transfer. Imagine a gas rapidly compressing or expanding in an insulated container.
  • Isobaric: occurs at constant pressure. An example of this is heating a gas in a piston that can expand while keeping the pressure constant.
  • Isochoric: occurs at constant volume. An example of this is heating a gas in a rigid container without expansion.

A thermodynamic cycle is a series of processes that returns the system to its initial state. The most common cycle is the Carnot cycle, which gives information about the efficiency of engines.

Laws of thermodynamics

The laws of thermodynamics provide a framework for understanding how energy flows and is transformed. These laws are fundamental principles in physics:

Zeroth law of thermodynamics

The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they will also be in thermal equilibrium with each other. This law helps define temperature.

Imagine three blocks of metal labeled A, B, and C. If blocks A and B are at the same temperature as block C, then blocks A and B must also be at the same temperature.

First law of thermodynamics

The first law of thermodynamics is the statement of conservation of energy. It implies that energy can neither be created nor destroyed, it can only be converted from one form to another or transferred from one object to another.

ΔU = Q - W

Here, ΔU represents the change in internal energy of the system, Q is the heat added to the system, and W is the work done by the system.

For example, consider a gas in a cylinder with a piston. If heat is added to the gas, it can do work by pushing the piston out. The remaining energy increases the internal energy of the gas.

Second law of thermodynamics

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. Entropy is a measure of the disorder or randomness in a system.

This law implies that natural processes tend towards a state of maximum chaos or equilibrium. It also states that it is impossible to convert all the heat energy into work in a cycle.

Imagine a neatly arranged stack of papers. Without any outside intervention, it is more likely to become disorganized over time than it is to remain perfectly organized.

ΔS ≥ 0
Here, ΔS is the change in entropy. For reversible processes, ΔS = 0 For irreversible processes, ΔS > 0.

Third law of thermodynamics

The third law of thermodynamics states that as the temperature of a system approaches absolute zero, the entropy of the system approaches a constant minimum. Essentially, it is impossible to reach absolute zero by any physical process.

Absolute zero (0 Kelvin) is the theoretical point where the vibrational speed of particles is minimal, representing the state of lowest possible entropy.

Thermodynamic variables and equations

Understanding the key equations and relationships between variables is extremely important to further understand thermodynamics.

Ideal gas law

The ideal gas law relates the pressure, volume and temperature of an ideal gas. It is expressed as:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the universal gas constant, and T is the temperature in Kelvin.

Enthalpy

Enthalpy is a state function denoted by H, which is defined as:

H = U + PV

Where U is the internal energy, P is the pressure, and V is the volume. It represents the total heat content of a system at constant pressure.

Entropy and the Carnot cycle

A fundamental concept is entropy, which is important in the second law. The Carnot cycle, an idealized thermodynamic cycle, allows one to understand the maximum theoretical efficiency of heat engines.

η = 1 - (T_c / T_h)

Here, η is the efficiency, T_c is the temperature of the cold storage, and T_h is the temperature of the hot storage.

Applications of thermodynamics

Thermodynamics has applications in a variety of fields; understanding these may make its importance clear:

Heat engine

Heat engines convert heat energy into mechanical work. Examples include car engines and steam turbines.

In a car engine, the combustion of fuel generates high temperatures, which creates pressure that moves a piston, producing mechanical work.

Refrigerators and heat pumps

Refrigerators use the principles of thermodynamics to transfer heat from a colder place to a warmer place, keeping the contents cool.

A heat pump does the opposite, using energy to transfer heat to warm a space.

Phase transition

Thermodynamics explains phase changes such as melting, boiling, and freezing, which involve entropy changes.

For example, heat energy is used to melt ice to form water, which changes the state from a solid to a liquid.

Visual explanation example

Expansion of gas in the piston

Consider an experiment in which a gas is confined in a cylinder containing a moving piston.

Initially, the gas is compressed, keeping the piston in the down position:

__ | |__ | | | | | | |__| |__
__ | |__ | | | | | | |__| |__

When heat is added, the gas expands, pushing the piston upward:

 __ | | | | | |____ |__| |
 __ | | | | | |____ |__| |

This view shows how energy transformations occur in thermodynamic processes, and also clarifies the concept of work done by a system.

Conclusion

Thermodynamics provides a lens through which we can explore how energy interacts with the world. From its basic concepts to its overarching laws, understanding thermodynamics opens the door to advancement in science and engineering. By exploring real-world applications such as engines, refrigerators, and natural processes, we see the important role thermodynamics plays in shaping our daily lives. As we continue to study these principles, we can innovate and optimize technologies that improve our understanding of energy and efficiency in the universe.

The complexities of thermodynamics demand further exploration, but even these elementary concepts and laws give us a profound understanding of the intricate dance between energy and matter.


Undergraduate → 3


U
username
0%
completed in Undergraduate

← Prev (2.5.5)
Electromagnetic waves
Next (3.1) →
Laws of Thermodynamics

Comments 



Thermodynamics

https://www.physicsflow.com/ug/3?pfal=en