Key Concepts in Thermodynamics

Definition: Thermodynamics is the branch of physics that deals with heat, work, temperature, and energy.
Laws of Thermodynamics:
1. Zeroth Law: If two systems are in thermal equilibrium with a third system, they are in equilibrium with each other.
2. First Law: Energy cannot be created or destroyed, only transformed (ΔU = Q - W).
  - ΔU: Change in internal energy
  - Q: Heat added to the system
  - W: Work done by the system
3. Second Law: The total entropy of an isolated system can never decrease over time. Heat cannot spontaneously flow from a colder body to a hotter body.
  - Entropy: Measure of disorder or randomness in a system.
4. Third Law: As the temperature of a system approaches absolute zero, the entropy of a perfect crystal approaches zero.
Key Terms:
- Heat (Q): Energy transfer due to temperature difference.
- Work (W): Energy transfer resulting from a force acting over a distance.
- Internal Energy (U): Total energy contained within a system.
- Enthalpy (H): Total heat content of a system, defined as H = U + PV (P = pressure, V = volume).
- Entropy (S): A measure of the degree of disorder in a system.
Processes:
- Isothermal: Constant temperature (ΔT = 0).
- Adiabatic: No heat exchange with surroundings (Q = 0).
- Isochoric: Constant volume (W = 0).
- Isobaric: Constant pressure.
Thermodynamic Cycles:
- Carnot Cycle: Ideal reversible cycle, demonstrates maximum possible efficiency.
- Rankine Cycle: Used in steam engines, converts heat into work.
- Otto Cycle: Ideal cycle for gasoline engines.
Thermodynamic Systems:
- Open System: Exchanges energy and matter with the surroundings.
- Closed System: Exchanges energy but not matter.
- Isolated System: Does not exchange energy or matter.
Applications:
- Heat engines (converting heat into work).
- Refrigerators (removing heat from a cold reservoir).
- Chemical reactions (energy changes).
Efficiency: Ratio of useful output energy to input energy, often expressed as a percentage.
Heat Transfer Methods:
- Conduction: Heat transfer through solid materials.
- Convection: Heat transfer through fluid motion.
- Radiation: Heat transfer through electromagnetic waves.

Understanding these foundational concepts is essential for delving deeper into the principles and applications of thermodynamics in various scientific and engineering fields.

Thermodynamics

The study of how heat, work, temperature, and energy interact in physical systems

Laws of Thermodynamics

Zeroth Law: Two systems in thermal equilibrium with a third system are also in equilibrium with each other.
First Law: Energy cannot be created or destroyed, only transformed.
- ΔU: Change in internal energy
- Q: Heat added to the system
- W: Work done by the system
Second Law: The total entropy of an isolated system can never decrease; heat cannot spontaneously flow from a colder body to a hotter body.
Third Law: As the temperature of a system approaches absolute zero, the entropy of a perfect crystal approaches zero.

Key Terms

Heat (Q): Energy transfer due to temperature difference
Work (W): Energy transfer resulting from a force acting over a distance
Internal Energy (U): Total energy contained within a system
Enthalpy (H): Total heat content of a system, defined as H = U + PV (P = pressure, V = volume)
Entropy (S): A measure of the degree of disorder in a system

Processes

Isothermal: Constant temperature (ΔT = 0)
Adiabatic: No heat exchange with surroundings (Q = 0)
Isochoric: Constant volume (W = 0)
Isobaric: Constant pressure

Thermodynamic Cycles

Carnot Cycle: Ideal reversible cycle, demonstrates maximum possible efficiency
Rankine Cycle: Used in steam engines, converts heat into work
Otto Cycle: Ideal cycle for gasoline engines