Energy Stores and Transfers

• Energy exists in different 'stores'.
• Energy cannot be created or destroyed.
• Energy can be transferred, dissipated, or stored in various ways.
• Energy can remain in the same store for millions of years or just a fraction of a second.
• Energy transfers occur constantly.
• A change in a system results in a change in how energy is stored.

Examples of Energy Transfers

• A boat moving through water: chemical energy converts to kinetic energy.
• Water boiling in an electric kettle: electricity increases the internal energy of the element, which in turn increases the internal (thermal) energy of the water, raising its temperature.
• A swinging pirate ship ride: kinetic energy converts to gravitational potential energy.

Types of Energy Transfer

• Potential difference (voltage): measures the energy given to charge carriers in a circuit; measured in volts (V); voltage makes an electric current flow.
• Materials can 'give out' energy, reducing its internal energy, like infrared radiation from the Sun.
• 'Doing work' means energy is being transferred, illustrated by examples like a grazing cow, a firing catapult, and a boiling kettle.

Diagrams for Energy Transfer

• Transfer diagrams use boxes for energy stores and arrows for energy transfers.
• A transfer diagram for a child at the top of a slide: gravitational energy converts to kinetic and internal energy due to mechanical work and friction, increasing the child and slide's temperature.
• Sankey diagrams: start with one arrow splitting into multiple, showing how energy transfers into different stores. Useful when the amount of energy in each source is known. The arrow's width represents the amount of energy.