Unit 1 · Energy
Energy Stores & Systems
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Systems and stores
- A system is an object or group of objects. When a system changes, the way energy is stored changes
- The eight energy stores:
| Store | Energy is stored because of |
|---|---|
| Kinetic | an object moving |
| Gravitational potential | an object raised in a gravitational field |
| Elastic potential | an object stretched or compressed |
| Thermal | the temperature of an object (its particles' kinetic energy) |
| Chemical | bonds that can be rearranged: fuels, food, batteries |
| Magnetic | magnets that attract or repel |
| Electrostatic | charges that attract or repel |
| Nuclear | the nucleus of an atom |
- Energy is transferred between stores by four pathways: mechanically (a force doing work), electrically (a current doing work), by heating, and by radiation (light, sound, electromagnetic waves)
Describing the changes
| Situation | Energy stored before | Energy stored after |
|---|---|---|
| Object thrown upwards | kinetic store of the object | gravitational potential store; some thermal (air resistance) |
| Moving object hits an obstacle | kinetic store | thermal store of object and surroundings; some transferred by sound |
| Object accelerated by a constant force | chemical store (fuel or food) | kinetic store; some thermal by friction |
| Vehicle slowing down | kinetic store | thermal store of the brakes and surroundings |
| Water boiled in an electric kettle | energy transferred electrically from the mains | thermal store of the water (and kettle, and air) |
- The rule for any description: name the store that decreases, the store that increases, and the pathway between them