Energy Transfers and Stores

• Energy exists in different 'stores' and cannot be created or destroyed.
• Energy can be transferred, dissipated, or stored in different forms.
• Energy can remain in the same store for varying durations, from millions of years to fractions of a second.
• Energy transfers occur constantly; any system change affects how energy is stored.

Examples of Energy Transfers

• A boat moving through water, where chemical energy is converted into kinetic energy.
• Heating water in an electric kettle: electricity increases the internal energy of the element, raising the water's internal (thermal) energy and temperature.
• A swinging pirate ship ride converts kinetic energy into gravitational potential energy and vice versa.
• Types of energy transfer include:
  • By electricity
  • By heating
  • By waves
  • By a force moving an object

Potential Difference (Voltage)

• Potential difference (or voltage) measures the energy given to charge carriers in a circuit, measured in volts (V).
• Voltage between two points causes electric current to flow.
• Energy is 'given-out' by the material
• Internal energy decreases.
• Infrared radiation emitted from the Sun into space is an example.

'Work'

• 'Work' is the scientific term for energy transfer.
• Energy is transferred through actions like a cow grazing, a catapult firing, or a kettle boiling.

Energy Transfer Diagrams

• Diagrams can illustrate energy transfers between stores, such as transfer diagrams and Sankey diagrams.
• Transfer diagrams use boxes for energy stores and arrows for energy transfers.
• Example: A child on a slide converts gravitational energy into kinetic and internal energy due to mechanical work and friction.
  • Gravitational potential energy shifts to kinetic energy and internal energy (raising the temperature of the child and the slide).

Sankey Diagrams

• Sankey diagrams start as one arrow that splits to show how energy is transferred into different stores.
• Useful when the amount of energy in each source is known.
• Arrow width is scaled to represent the amount of energy.