Energy stores and transfers
Energy cannot be seen, but it sits in stores (kinetic, gravitational, thermal, chemical, elastic) and moves between them. It is measured in joules (J).
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Analogy
Money in different pockets: it moves between pockets, but the total stays the same.
Example
Electrical energy in.Thermal energy in the water.A little sound and heatescape to the room.
In practice
A phone battery holds energy in a chemical store. Using it moves energy to light, sound and heat.
Practice
Flashcards
- What is the unit of energy?The joule (J).
Questions people ask
What are the main energy stores?
The main stores are kinetic (moving), gravitational potential (height), elastic potential (stretched or squashed), chemical (food, fuel, batteries), thermal (heat in a material) and nuclear. Energy is always measured in joules, and it moves from one store to another when something happens.
What is the unit of energy?
The joule (J). One joule is the energy needed to lift a small apple, about 1 N, upwards by 1 metre. Larger amounts use kilojoules (kJ, 1,000 J) or megajoules (MJ, 1,000,000 J). A food label usually shows energy in kJ.