AP Physics 2
Advanced Placement Physics 2 focusing on fluids, thermodynamics, and modern physics.
Laws of Thermodynamics
Rules That Govern Energy
The laws of thermodynamics explain how energy is transferred and transformed. These principles are universal, applying to everything from engines to living cells.
The Four Laws
- Zeroth Law: If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other.
- First Law: Energy cannot be created or destroyed, only changed from one form to another (conservation of energy).
- Second Law: Entropy, or disorder, tends to increase in an isolated system. Heat naturally flows from hot to cold.
- Third Law: As temperature approaches absolute zero, entropy approaches a minimum.
Mathematical Expression
The First Law:
\( \Delta U = Q - W \)
where \( \Delta U \) is the change in internal energy, \( Q \) is heat added, and \( W \) is work done by the system.
Importance
These laws are the foundation for understanding engines, refrigerators, and the direction of natural processes.
Key Formula
\[\Delta U = Q - W\]
Examples
A steam engine converts heat from burning fuel into work that moves a train.
Sweating cools your body as water evaporates, increasing entropy.
In a Nutshell
The laws of thermodynamics set the limits for energy transfer and transformation.