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

1. Zeroth Law: If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other.
2. First Law: Energy cannot be created or destroyed, only changed from one form to another (conservation of energy).
3. Second Law: Entropy, or disorder, tends to increase in an isolated system. Heat naturally flows from hot to cold.
4. 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.