lecture 4

• Different forms of energy


  • Chemical Potential Energy
  • Potential Gravitational Energy
  • Kinetic Energy
  • Thermal Energy
  • Mass Energy
  • Electrical Energy
  • Electromagnetic Radiation Energy
  • Elastic Potential Energy
• Gravitational Potential Energy


  • Potential energy = energy of position in a force field (e.g. gravitational field)
  • Potential energy can be stored until released
  • Lose potential energy when released - but gain kinetic energy
• Gravitational Potential Energy


  • Hydropower
• Chemical Potential Energy


  • Internal energy of chemical bonds => energy is stored in the chemical bonds
  • Energy can be is released by chemical reactions giving off heat (exothermic) or a chemical reaction can take up heat (endothermic)
  • Chemical Potential Energy can be converted to mechanical energy
• Chemical Potential Energy


  • Combustion of fuels such as wood, coal, oil, gas
  • Human metabolism fueled by food
  • Photosynthesis
• Fossil Fuels


  "Fossil sunlight" stored in the chemical bonds of hydrocarbons, and are most commonly used sources for energy generation in today's society (85% of all primary energy)
• Kinetic Energy


  • Kinetic energy (K) = "Mass in motion"
  • Work is needed to bring a car up to speed (by combusting the gasoline)
  • Car at speed has kinetic energy, so does a running person or a falling apple
• Kinetic Energy


  • Kinetic energy of the wind drives the wind turbines
• Mass Energy


  • Mass can be converted to Energy and vice versa
  • Fission energy => splitting of an atom => resulting products have slightly less mass, this loss of mass is turned into energy
• Mass Energy


  • Atomic power plants
• Electric Potential Energy


  • An electric charge is taken to higher electric potential (i.e. higher voltage, V)
  • Release of 'potential electrical energy' to some other form – heat, mechanical etc
  • Very useful way of storing and transporting energy – can be used for anything
• Thermal Energy (Heat energy)


  • Random molecular motion within any medium
  • The heat puts the molecules in an object in motion = kinetic energy of individual molecules increase
  • Related to temperature (but temperature is not = energy)
  • Heat flows from warm to cold
• Electromagnetic Radiation


  • Emitted from the sun – never ending!
  • Planck's constant (h); speed of light (c); wavelength (λ)
  • 99.98% of all energy flows and fuels on earth comes from the Sun!
• Earth's energy flows and fuels (99.98% from the sun)
• How much is 1017W?
• Energy conversions: from the sun to your TV


  1. Mass energy

  2. Electromagnetic radiation energy

  3. Chemical energy

  4. Heat energy

  5. Chemical energy

  6. Heat energy

  7. Kinetic energy

  8. Electrical energy

  9. Photosynthesis

  10. Electrical energy

  11. Heat energy