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General energy conservation
Intermediate
Total energy including heat and other forms is conserved.
Energy is never destroyed, only transferred or transformed: mechanical, thermal, chemical, electrical and so on. The total in an isolated system stays constant.
A car's fuel energy goes into motion, heat in the engine and sound.
"Energy loss" means conversion into forms we can't use.
In more detail
The law of conservation of energy states that energy is neither created nor destroyed, but changes from one form to another. Including thermal, chemical and nuclear energy keeps the total constant.
Real-world uses
- Power stations convert chemical energy in fuel into electrical energy and heat.
- Batteries convert chemical energy to electrical energy when they power a device.
- Thermal power plants trace all their energy input to electricity, heat and waste, showing total energy is conserved.
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Frequently asked questions
Is energy ever created?
No. Apparent creation is always a conversion from another form.
Why do we say energy is 'lost'?
Because it becomes less useful, usually as low-grade heat, not because it disappears.
Is energy ever created or destroyed?
No. Energy is conserved overall. It changes form, and any apparent loss is a transfer to another store, such as heat.
Related topics in Work, Energy & Power
Energy in spring-mass systems · Roller coaster and loops · Energy loss to friction · Power · Instantaneous power · Units of power