Knowledge Organiser: Energy Stores and Systems
Key Terms
- Energy store: where energy is held (kinetic, GPE, elastic, chemical, thermal, magnetic, electrostatic, nuclear)
- Pathway: how energy moves (mechanical, electrical, heating, radiation)
- Dissipation: spreading energy to thermal store of surroundings
- Closed system: no energy in or out; total stays constant
Key Facts
- Energy cannot be created or destroyed — only transferred
- There are 8 energy stores and 4 transfer pathways
- Wasted energy nearly always goes to the thermal store
- The total energy in a closed system is always conserved
The 8 Stores (KGETMENCC)
- Kinetic, Gravitational PE, Elastic PE, Thermal
- Magnetic, Electrostatic, Nuclear, Chemical
- Mnemonic: Kicking Giraffes Eat Thirteen Million Electric Newts Carelessly
Exam Tips
- Never say energy is "lost" — say it is "dissipated to thermal store"
- Always name both the store AND the pathway in transfer questions
- In Sankey diagrams, arrow widths must be proportional to energy values
- Height must be vertical when calculating GPE
Key Equations
- Eₖ = ½ × m × v² (kinetic energy)
- Eₚ = m × g × h (gravitational potential energy)
- Eₑ = ½ × k × x² (elastic potential energy)
- ΔE = m × c × ΔT (change in thermal energy)
- E = P × t (energy = power × time)
Common Mistakes
- Saying energy is "lost": Energy is always conserved — say it is "dissipated to the thermal store of the surroundings"
- Confusing stores and pathways: Kinetic is a store; mechanical work is a pathway — they are not the same thing
- Forgetting wasted energy: Always mention wasted energy (usually thermal) when describing transfers in real systems
- Vague descriptions: "light energy" loses marks — say "radiated from the bulb as light"
- Sankey diagram widths: Arrow widths must be drawn proportional to the energy values — not equal width
Memory Aid
- Kinetic, Gravitational, Elastic, Thermal, Magnetic, Electrostatic, Nuclear, Chemical
- Mnemonic: "Kicking Giraffes Eat Thirteen Million Electric Newts Carelessly"
- And the 4 transfer pathways: Mechanical, Electrical, Heating, Radiation — remember "MEHR"