Lessons · Teaching · energy, and the fact that it is never made
Energy is transferred and never made
Energy comes in forms: kinetic in movement, potential in position, thermal, light, sound, electrical and chemical. It is never created or destroyed, only transferred and changed in form, and some of it always ends up as heat spread out too thinly to use.
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In beta. This lesson was written for Hone and has not yet been checked by a state certification officer. Practice material, not professional advice. What that means.
What it is for
'Using up' energy is the everyday phrase and it is wrong in a way that matters. A light bulb does not consume energy; it turns electrical energy into light and heat. Saying that precisely is what lets a class trace energy through anything they are shown.
How to think about it
For any device or event, write the chain: what form went in, what forms came out, and where the waste went. There is always waste, and it is almost always heat. Naming the waste is what completes the answer.
Worked example
A torch: chemical in the battery to electrical to light, with heat as wasteThree forms and a loss, in one sentence.
A ball thrown up: kinetic becomes potential at the top, then back to kineticThe total stays the same, ignoring air resistance.
Food is chemical energy, released in your cells by respirationWhich joins this lesson to the first one on the road.
Energy is never used up, only moved and changed, with some always spread out as heatWhich is why no machine is ever fully efficient.
Your turn
Name the form of energy that an object has because it is moving.
Movement energy is called energy
Solve one, graded on the server
The trap
Calling electricity a form of energy source rather than a transfer. Electrical energy has to come from somewhere: chemical in a battery, or whatever turned the generator.