7.1Physics 01. Forces And Energy
Energy changes from events or processes and energy dissipates and… — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions
5 min read 9 parts Lesson 1 of 12 1 quiz
Lesson summary
7.1 Energy stores, energy changes and dissipation — CHECKPOINT - Lower Secondary Science 0893 notes: Describe energy changes in events and processes, and explain that some energy is dissipated and becomes less useful.Energy — something that must be changed or transferred in order…
- Long-lasting stores
- Short-lasting stores
- Process or event
- Useful energy
- Wasted energy
- Dissipated energy
Section 1 of 9What energy is
Energy
- Energy something that must be changed or transferred in order for anything to happen.
Unit
- Unit energy is measured in joules (J).
Section 2 of 9Energy stores and transfers
| Energy | Description | Store or transfer |
|---|---|---|
| Kinetic | Energy of a moving object | Store |
| Chemical | Energy stored in food, fuels and batteries | Store |
| Gravitational potential | Energy stored when an object is lifted | Store |
| Elastic potential | Energy stored when an object is stretched or squeezed | Store |
| Thermal | Energy of hot objects, moves to colder objects | Store or transfer |
| Electrical | Energy carried by current in a circuit | Transfer |
| Sound | Energy transferred by vibrating objects | Transfer |
| Light | Energy from luminous objects | Transfer |
Section 3 of 9Storing energy
Long-lasting stores
- Long-lasting stores chemical energy in rice, coal, crude oil and batteries, and gravitational potential energy of lifted water.
Short-lasting stores
- Short-lasting stores thermal energy, because hot objects cool down, and kinetic energy, because moving objects stop.
Section 4 of 9Energy changes in events and processes
1Process or event
- Process or event an energy change happens when something happens.
2Examples
- Examples burning wood changes chemical energy to thermal energy and a falling book changes gravitational potential energy to kinetic energy.
Section 5 of 9Examples of useful energy changes
| Device or action | Useful energy change |
|---|---|
| Fire burning wood | Chemical to thermal |
| Television | Electrical to light and sound |
| Candle | Chemical to light |
| Walking up stairs | Chemical to kinetic to gravitational potential |
| Power station | Chemical to thermal to kinetic to electrical |
Section 6 of 9Useful and wasted energy
Useful energy
- Useful energy the energy changed in the way we want.
Wasted energy
- Wasted energy energy changed into forms that are not wanted, mostly thermal and sound.
Examples
- Examples a motorcycle engine changes only about 25% of the fuel's chemical energy to kinetic energy.
- A lamp A changes about 15% of the electrical energy to light and lamp B changes about 50%.
Section 7 of 9Dissipation
Dissipated energy
- Dissipated energy energy that spreads out into the surroundings where it has no use.
Not recoverable
- Not recoverable dissipated thermal and sound energy cannot be gathered and used again.
Always
- Always every energy change wastes some thermal energy.
Section 8 of 9Key terms
| Term | Meaning |
|---|---|
| Energy | What is changed or transferred to make something happen. |
| Joule | Unit of energy. |
| Kinetic energy | Energy stored in a moving object. |
| Chemical energy | Energy stored in fuels, food and batteries. |
| Dissipated | Spread out into the surroundings and less useful. |
| Wasted energy | Energy changed to forms that are not useful. |
Section 9 of 9Exam technique
1
Energy is used up — energy is changed or transferred and the total stays the same.
2
Wasted energy disappears — it is dissipated into the surroundings.
3
Hot and cold are energy stores — thermal energy is the store, and cold means less thermal energy.
4
Only machines waste energy — every energy change dissipates some energy.
Marked practiceQuizzes for this lesson
Last updated: