Conservation of Energy | Physics for GCSE/IGCSE - Year 11 PDF Download

Conservation of Energy

• The conservation of energy principle asserts that energy cannot be created nor destroyed; rather, it can only transition between different energy stores.
• In essence, for a closed system, the total energy remains constant over time.
• The total energy inputted into the system equals the total energy outputted from it.
• Consequently, energy cannot vanish; however, it can be transferred to the surroundings.
  • Energy dispersion to the surroundings commonly occurs through processes like heating and radiation.
  • These dissipated energy transfers are frequently non-utilizable and are thus referred to as wasted energy.

Energy Flow Diagrams

• Energy stores and transfers can be illustrated through a flow diagram.
• Such a diagram visually represents both the various energy stores and the transfers occurring within a system.

Energy flow diagram showing energy stores and transfers in a nuclear power plant.

Sankey Diagrams

• Sankey diagrams are a visual tool that illustrates energy transfers. They are characterized by arrows that split to show the proportions of energy moving between different components.
• The different segments of a Sankey diagram represent various energy transfers:
  • The left side of the arrow (the flat end) symbolizes the energy entering the system.
  • The straight arrow pointing right depicts the energy that is utilized or ends up in the intended destination, which is the useful energy output.
  • Arrows bending away signify the energy that is wasted.

• The width of each arrow in a Sankey diagram corresponds to the amount of energy being transferred.
• Energy conservation principle holds: Total energy in = Useful energy out + Wasted energy
• A Sankey diagram for a modern efficient light bulb differs significantly from that of an old filament bulb.
• A more efficient bulb shows less wasted energy, depicted by a smaller downward arrow representing heat energy.