What is conservation of energy?

Conservation of energy: Energy in = energy out. Energy is never made and never destroyed: it only changes from one form to another. Add up every form, height, motion, heat, chemical, electrical and even mass, and the total always stays the same.

Read how it works: What is conservation of energy? · The history of the conservation of energy · More boxes on Glassbox

Chapters in this interactive model

1. Energy changes form, the total never changes: Height becomes speed, speed becomes height, and friction turns a little into heat.
2. Fuel, food and brakes: Every journey turns stored energy into motion, and every stop turns motion into heat.
3. Electricity in, heat out: A geyser and a microwave: every joule of electricity ends up as heat, just not all where you want it.
4. Storing energy, and moving heat: A battery pays back less than you put in. An AC seems to give more than it takes. Both keep the books.
5. No free energy, and mass is energy too: Why perpetual-motion machines always stop, how the Sun turns mass into light, and why energy is conserved at all.