Thermodynamics

• The First Law of Thermodynamics:
  • This law is a statement of the principle of conservation of energy. It states that energy can neither be created nor destroyed but only transferred from one form to another.
  • The total amount of energy in a closed system (one that does not exchange energy with its surroundings) remains constant.
• The Second Law of Thermodynamics:
  • This law deals with the concept of entropy, a measure of disorder in a system.
  • A system with high entropy is more disordered than a system with low entropy. The second law states that in an isolated system (one that does not exchange matter or energy with its surroundings), entropy always increases over time.
  • This means that usable energy tends to disperse over time into less usable forms, leading to a gradual increase in disorder.
  • Entropy can be understood as a measure of how spread out or disorganized the energy in a system is. Over time, energy tends to disperse from concentrated usable forms to more spread-out unusable forms, increasing the overall disorder.
• These two laws of thermodynamics have been extensively tested and verified through experiments.

Major contributors

• Major contributors to the laws of thermodynamics were Nicolas Léonard Sadi Carnot, James Prescott Joule and Lord Kelvin all of whom were at work during the 19^th century.
  • Nicolas Léonard Sadi Carnot (1796-1832) was a French physicist and engineer. He is best known for his work on thermodynamics, particularly his development of the Carnot cycle, a theoretical thermodynamic cycle that describes the maximum efficiency of a heat engine.
  • James Prescott Joule (1818-1889) was an English physicist and brewer. He is best known for his work on the relationship between heat and work, which led to the development of the first law of thermodynamics.
  • William Thomson, 1st Baron Kelvin (1824-1907) was a Scottish mathematician, physicist and engineer. He is best known for his work on thermodynamics, particularly his development of the Kelvin scale of temperature.

Examples of thermodynamics

• The First Law in Action:
  • Imagine throwing a ball up in the air. As the ball rises, its kinetic energy of motion is converted into potential energy due to its height.
  • When the ball falls back down, the potential energy is converted back into kinetic energy.
  • Even though the form of the energy changes (kinetic to potential and back), the total amount of energy in the ball remains constant.
  • This exemplifies the principle of energy conservation as described by the first law of thermodynamics.
• The Second Law in Action:
  • Consider a light bulb. When you turn it on, the electrical energy from the outlet is transformed into light energy and thermal energy (heat).
  • The total amount of energy is still conserved, following the first law.
  • However, the light bulb’s heat dissipates into the surroundings, making it less concentrated and usable.
  • Heat energy, in this sense, is more spread out and less usable than electrical energy, making the system more disordered according to the second law of thermodynamics. Entropy, a measure of disorder, therefore increases in this process.