Thermal Energy and Heat Transfer - Revision Sheet

1. 📌 Essentials

• Thermal energy: Total kinetic energy of particles in a substance.
• Temperature: Average kinetic energy per particle; measured in °C or K.
• Heat: Energy transferred between systems due to temperature difference.
• Modes of heat transfer: conduction, convection, radiation.
• Thermal expansion: Materials expand when heated; linear and volume expansion formulas.
• Specific heat capacity: $Q = mc\Delta T$; energy needed to change temperature.
• Latent heat: Energy involved during phase changes (fusion, vaporization) without temperature change.
• fan-Boltzmann law: Power radiated $P = \sigma e A T^4$.
• Fourier’s law: Heat transfer rate depends on thermal conductivity, temperature gradient, and area.
• Practical relevance: Insulation, heating, cooling, thermal management.

. 🧩 Key Structures & Components

• Particles: Constitute matter; kinetic energy relates to temperature.
• Thermal energy: Sum of particles' kinetic energies.
• Temperature scales:
  • Celsius: 0°C (freezing), 100°C (boiling).
  • Kelvin: 0 K (absolute zero, -273.15°C).
• Heat transfer mediums:
  • Solids: conduct heat.
  • Fluids: transfer via convection.
  • Electromagnetic waves: transfer via radiation.
• Materials’ thermal properties:
  • Conductivity ($k$)
  • Expansion coefficients ($\alpha$, $\beta$)
  • Emissivity ($e$)

---