Energy
Energy Stores and Systems
AQA GCSE Physics
A system
- A system is a group of objects that interact, or a single object.
- Energy is transferred between the stores of the objects in a system when it changes.
Energy stores
- chemical, kinetic, gravitational potential, elastic potential, thermal
- The thermal store is also called the internal energy store.
Changes in energy stores (common situations)
| Situation | Store that decreases | Store that increases |
|---|---|---|
| Fuel or food used to make something move | chemical | kinetic |
| An object falling | gravitational potential | kinetic |
| An object projected upwards | kinetic | gravitational potential |
| A stretched spring or cord released | elastic potential | kinetic |
| An object accelerated by a constant force | Store of the object or system supplying the force | kinetic |
| A vehicle slowing down | kinetic | thermal (brakes and surroundings) |
| An object hitting an obstacle | kinetic | thermal |
| Water heated in an electric kettle | chemical | thermal |
- A moving object that slows because air resistance opposes the motion of the object: energy is transferred to the surroundings.
- Work done against air resistance causes thermal energy to be transferred to the surroundings.
Ways energy is transferred
| Pathway | What transfers the energy |
|---|---|
| Heating | A temperature difference |
| Work done by forces | A force moving an object |
| Work done when a current flows | Charge moving in a circuit |
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