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Heat: An Ever-Present Force

  • Context (TH): Heat has been present since the birth of the universe and will persist until its death.
  • The Industrial Revolution, fueled by steam-powered engines, exemplifies its transformative power.

Heat – Basics

  • At the microscopic level, temperature is the average kinetic energy of an object’s constituent particles.
  • Heat flows from hotter to colder objects until they reach equilibrium.
  • It is a form of energy studied through thermodynamics and statistical mechanics. It can be transferred within a medium and used for various applications.

Heat, Work, and Entropy

  • Heat and work have the same physical dimensions, but not all heat can be converted into useful work.
  • Entropy represents the disorderliness in a system, preventing heat from contributing to useful work.
  • Adiabatic processes involve work without heat exchange and are reversible.

Applications of Heat

Internal Combustion Engines (ICEs)

  • ICEs convert heat to mechanical work, exemplifying the practical application of the theoretical Carnot cycle (a theoretical model for maximum efficiency in converting heat to work).
  • Cycle involves 4 steps: isothermal expansion & compression, and isentropic expansion & compression.
  • Each step manipulates the temperature and pressure of a gas to extract work.

Thermal Power Plants

  • Thermal Power plants utilise the Rankine cycle, which also operates in four steps: isentropic compression, heat addition, isentropic expansion, and heat removal.
  • Heat from sources like coal is used to generate steam, which drives turbines to produce power.
  • In Isentropic Expansion gas or vapour expands adiabatically (no heat transfer to or from the surroundings) and reversibly. In Isentropic Compression, gas or vapour is compressed adiabatically.
  • During both the process, the entropy of the system remains constant, hence the term “isentropic.

Other Applications

  • Metallurgy and Materials Science: Heat treatments are crucial for shaping and strengthening materials.
  • Mining and Refineries: Heat is used in various processes for extracting and refining resources.
  • Chemical Reactions: Many chemical reactions require specific heat conditions to proceed.
  • Meteorology: Heat transfer in the atmosphere drives weather patterns.
  • Transportation: Heat engines power vehicles like cars and aeroplanes.
  • HVAC Systems: Heat is used to heat buildings and cool them through refrigeration or ACs.

Heat and Climate Change

  • The global response to climate change involves two main strategies: mitigation and adaptation.
  • Mitigation involves reducing greenhouse gas emissions that trap heat and contribute to global warming.
  • Researchers are developing new ways to produce heat energy without fossil fuel combustion or reducing emissions from existing technologies.
  • Adaptation involves preparing for the consequences of rising temperatures, such as heat waves. This includes improving public health measures and infrastructure to cope with extreme heat.

Role of Heat in Geography

  • Heat drives climate and weather patterns, causing temperature, air pressure, and density differences that lead to atmospheric circulation and weather events like winds, clouds, and precipitation.
  • Heat is essential for the hydrological cycle through evaporation.
  • Heat influences rock weathering, with high temperatures causing mechanical breakdown and accelerating chemical weathering processes, thereby influencing landform development.
  • The Earth’s internal heat also drives the evolution of landforms through glacier melting, tectonic plate movement, and volcanic activity.
  • Heat determines plant and animal distribution, influencing species survival and ecosystem diversity.
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