Thermodynamics: Basic Concepts

• Physics is a natural science examining matter, its fundamental parts, motion and behavior across space and time, alongside related concepts like energy and force.
• Physics aims to understand the behavior of the universe.

Thermodynamics

• Thermodynamics studies energy, particularly heat, and its connections to other energy forms namely mechanical, electrical, or chemical energy.
• Focuses on macroscopic system properties such as temperature, volume, and pressure.
• It does not focus on matter's microscopic components.

Basic Concepts

• System: A specific space or quantity of matter.
• Surroundings: Everything external to the system.
• Boundary: The system's separating surface from its surroundings.
  • System types:
    • Isolated system: No exchange of matter or energy occurs with the surroundings.
    • Closed system: Energy exchange can occur, but matter cannot.
    • Open system: Both energy and matter can be exchanged.
• Thermodynamic properties: System-defining characteristics.
  • Intensive properties: These are not affected by the substance amount, this includes temperature, pressure, and density.
  • Extensive properties: These depend on the amount of substance and include mass, volume, and energy.
• Thermodynamic equilibrium: This is when system properties are unchanging and uniform over time.

Laws of Thermodynamics

• Zeroth Law: Two systems in thermal equilibrium with a third are also in equilibrium with each other.
• First Law: Energy remains constant and cannot be created or destroyed; a system's internal energy change equals the net heat added minus net work done (ΔU = Q - W).
  • Internal energy (U): A system's total energy, stemming from molecular kinetic and potential energies.
  • Heat (Q): Energy transferred due to temperature differences.
  • Work (W): Energy transferred by a force causing displacement.
• Second Law: An isolated system's total entropy can only increase or stay constant in ideal scenarios.
  • Entropy (S): Indicates a system's disorder or randomness.
  • Processes generally increase the entropy of the system and its surroundings.
• Third Law: Entropy approaches a minimum or zero figure as temperature nears absolute zero.

Thermodynamic Processes

• Isothermal process: Happens at a consistent temperature.
• Isobaric process: Takes place at constant pressure.
• Isochoric/Isometric process: Occurs at constant volume.
• Adiabatic process: Happens without heat transfer (Q = 0).

Electromagnetism

• Electromagnetism is the examination of electromagnetic forces that occur between charged particles.
• It is a fundamental force behind everyday phenomena, excluding gravity and nuclear activities.

Basic Concepts

• Electric charge: A fundamental matter property causing electric forces.
  • Includes positive and negative charges.
  • Like charges repel; opposites attract.
  • Measured in coulombs (C).
• Electric field: The area around an electric charge where another charge will experience a force.
  • Represented via electric field lines.
  • Field direction aligns with the force on a positive test charge.
• Electric potential: Electrical potential energy per charge unit at a location.
  • Measured in volts (V).
• Current: The electric charge flow rate.
  • Measured in amperes (A).
• Voltage: The potential difference between two points in a circuit.
• Resistance: Opposition to current flow.
  • Measured in ohms (Ω).

Key Laws

• Coulomb's Law: Force between two charges is proportional to their magnitude product and inversely proportional to the square of their distance.
• Ohm's Law: Voltage across a resistor is directly proportional to the current flowing through it (V = IR).
• Faraday's Law of Induction: A changing magnetic field generates an electromotive force (EMF) in a circuit.

Magnetism

• Magnetic field: A force field created by moving electric charges (current) and magnetic substances.
  • Represented via magnetic field lines.
  • Magnetic fields apply forces on moving charges.
• Magnetic dipole moment: Measures a magnetic source's strength and orientation.
• Electromagnets: Magnets produced by electric currents.

Maxwell's Equations

• Gauss's Law for Electricity: Connects the electric field to electric charge distribution.
• Gauss's Law for Magnetism: Disproves the existence of magnetic monopoles.
• Faraday's Law of Induction: An electric field is produced by a changing magnetic field.
• Ampère-Maxwell Law: Connects the magnetic field to electric current and changing electric fields.

Electromagnetic Waves

• Electromagnetic waves are disturbances propagating through space via electric and magnetic field interactions.
• These travel at the speed of light (c ≈ 3.0 x 10^8 m/s).
• Examples: Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Quantum Physics

• Quantum physics studies extremely small elements: atoms and subatomic particles.
• It shows that energy, momentum, angular momentum, and other bounded system quantities have discrete values (quantization).
• Quantum mechanics details how matter and energy act at atomic and subatomic levels.

Basic Concepts

• Quantization: Certain physical properties can only have set discrete values.
• Wave-particle duality: Particles behave like waves, and waves behave like particles.
• Uncertainty principle: Precisely knowing a particle's position and momentum at the same time is impossible.
• Superposition: A quantum system exists in multiple states simultaneously.
• Quantum entanglement: Linked particles instantly affect each other, regardless of distance.

Key Concepts

• Planck's constant (h): A constant relating a photon's energy to its frequency.
• Photon: A light particle with energy E = hf, where f is frequency.
• Schrödinger equation: The basic quantum mechanics equation detailing quantum system evolution.
• Quantum numbers: Numbers defining the allowed states of a quantum system.
• Atomic structure: Atoms have a nucleus (protons and neutrons) encircled by electrons.
• Quantum field theory: Unites quantum mechanics and special relativity to explain forces and particles.

Applications

• Lasers
• Transistors
• Medical imaging (MRI)
• Nuclear energy

Relativity

• Relativity, developed by Albert Einstein, revolutionized our understanding of space, time, and gravity.

Special Relativity

• Postulates:
  • Physics laws remain consistent for all observers in uniform motion.
  • Light speed is constant for all inertial observers, irrespective of light source motion.
• Consequences:
  • Time dilation: Moving observers experience time slower relative to stationary ones.
  • Length contraction: Moving observers see object lengths shortened in their motion direction.
  • Mass increase: An object's mass rises as its velocity nears light speed.
  • Mass-energy equivalence: Energy and mass are interchangeable (E = mc^2).
  • Relativity of simultaneity: Simultaneous events in one reference frame may not be in another.

General Relativity

• Postulate:
  • Equivalence principle: Gravitational and inertial forces are indistinguishable.
• Concepts:
  • Gravity is spacetime curvature caused by mass and energy, not a force.
  • Gravitational lensing: Light bends around massive objects.
  • Gravitational time dilation: Stronger gravitational fields slow time.
  • Black holes: Spacetime areas with extreme gravity, preventing anything, including light, from escaping.
  • Gravitational waves: Spacetime ripples from accelerating massive objects.