Energy Transfer
Year 7 🌡️ Energy & Thermodynamics Describe energy stores and pathways; understand conservation of energy.
🔋 Energy Stores
Energy is stored in different objects and systems. We describe these as energy stores.
| 🗃️ Store | 📝 Description | 🔍 Example |
|---|---|---|
| ⚡ Kinetic | Energy of moving objects | Rolling ball, running child |
| 🌍 Gravitational PE | Energy due to height | Book on a shelf, water in dam |
| 🌀 Elastic PE | Energy stored in stretched/compressed objects | Spring, stretched elastic band |
| 🔥 Thermal | Internal energy of hot objects | Hot water, burning coal |
| 🔋 Chemical | Energy stored in chemical bonds | Food, batteries, fuel |
| ☢️ Nuclear | Energy stored in atomic nuclei | Uranium, plutonium |
| 💡 Electromagnetic | Energy carried by light/EM waves | Sunlight, radio signals |
⚡ Transfer Pathways
Energy moves between stores using four transfer pathways: mechanical work, electrical work, heating, and radiation.
| 🔄 Pathway | 📝 How it works | 🔍 Example |
|---|---|---|
| 💪 Mechanical work | A force moves an object | Pushing a box up a ramp |
| ⚡ Electrical work | Charge flows through a circuit | Charging your phone |
| 🌡️ Heating | Thermal energy passes from hot to cold | Warming hands on a mug |
| 🌊 Radiation | EM waves carry energy | Sunlight warming the Earth |
🔦 Torch example: Chemical store (battery) → electrical pathway → light radiation + thermal store (waste heat)
⚽ Kicked ball: Chemical store (leg muscles) → kinetic store → gravitational PE (when it rises) → kinetic (comes down)
♻️ Conservation of Energy
Energy is never created or destroyed — it is only transferred between stores or dissipated as heat.
⚡ Law of Conservation of Energy
$$\text{Total energy input} = \text{useful energy output} + \text{wasted energy}$$ In the real world, some energy is always wasted as heat — no machine is 100% efficient!
💡 LED bulb: Takes in 10 J of electrical energy, gives out 9 J as light, wastes 1 J as heat. Efficiency = 90%.
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
🔋 Energy Transfer Calculator
Calculate kinetic energy (KE) and gravitational potential energy (GPE).