Thermodynamics Lecture Notes

Drinking Bird Toy

• Demonstrates thermodynamics principles.
• Appears as a perpetual motion machine, but isn't due to energy laws.

First Law of Thermodynamics

• Describes the transfer of energy: work and heat.
• Equation: Internal Energy (U) = Heat (Q) - Work (W).
• Sign Convention:
  • Q is positive when heat is added to the system.
  • W is positive when work is done by the system.

Types of Thermodynamic Processes

1. Isovolumetric Processes

• Volume constant, heat is added/removed.
• Pressure and temperature change; no work done.

2. Isobaric Processes

• Pressure constant; volume and temperature change.
• Work done = pressure x change in volume.
• System does work when heat is added; work done on system when compressed.

3. Isothermal Processes

• Temperature constant using a heat reservoir.
• Pressure changes require integration to calculate work.
• No change in internal energy; heat added equals work done.

4. Adiabatic Processes

• No heat flow; gas can expand/compress.
• Change in internal energy = - work done.

Second Law of Thermodynamics

• Heat flows from hot to cold (spontaneously).
• Related to entropy (system disorder).
  • Entropy increases overall in the universe.
  • Probability and molecular arrangements explain entropy increase.
• Entropy increases cause heat flow, illustrated by the drinking bird.

Entropy

• Probability-driven concept.
• Orderly states (lower entropy) are less probable than disordered ones (higher entropy).

Applications

• Machines & Engines:
  • Variations in thermodynamic processes crucial in engines.

Additional Notes

• Crash Course Physics association with PBS Digital Studios.
• Additional learning resources available on PBS Digital Studios’ channel.