Energy Transfers and Stores

• Energy exists in different 'stores'.
• Energy cannot be created or destroyed.
• Energy can be transferred, dissipated, or stored in different ways.
• Energy can remain in the same store for millions of years or just a fraction of a second.
• Energy transfers occur constantly whenever a system changes.

Examples of Energy Transfers

• A boat moving through water: Chemical energy transforms into kinetic energy.
• Boiling water in an electric kettle: Electricity increases the internal energy of the heating element, which in turn increases the water's internal (thermal) energy, raising its temperature.
• Swinging pirate ship ride: Kinetic energy converts into gravitational potential energy.

Types of Energy Transfer

• Heating
• Waves
• Electric current
• A force moving an object

Potential Difference (Voltage)

• Potential difference (or voltage) measures the energy given to the charge carriers in a circuit.
• Units of potential difference = volts (V).
• Voltage exists between two points and causes electric current to flow.
• Energy is released by the material, decreasing its internal energy.
• Infrared radiation from the Sun is emitted into space.
• 'Work' in science means energy has been transferred.

Transfer Diagrams

• Transfer diagrams illustrate energy transfers from one store to another.
• Boxes represent energy stores, and arrows represent energy transfers.
• Example: A child at the top of a slide.
• Gravitational energy stored in the child is transferred into kinetic energy (speeding up) and internal energy (overcoming friction).
• Energy shifts from gravitational potential energy to kinetic energy and internal energy (raising the temperature of the child and the slide).

Sankey Diagrams

• Sankey diagrams begin as a single arrow that splits into multiple points.
• Represents how energy in a system is transferred into different stores.
• Useful when the amount of energy in each source is known.
• The width of the arrows is proportional to the amount of energy.