• Pixel-art sticker of Effio, personifying Energy Efficiency, with the caption “Not All Energy Does The Job.”

IndexHeat & EntropySticker

Effio

Energy Efficiency Physics

\[\eta = \frac{E_{\text{out}}}{E_{\text{in}}}\]
$4.99 USD
$4.99 USD
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Meet Effio, a light bulb who turns some of his energy into light and loses the rest as heat. Efficiency is useful energy out divided by total energy in. Take in 60 J, give out 6 J of light, and he is 10% efficient; the other 54 J warms the room. Pixel-art kiss-cut sticker in 2, 3, 4 and 6 inches; equation, symbols and sources in the physics panel below.

Size
Surface

Flat $6 shipping worldwideMade to order, ships in 2–5 business days

Details

Size3″ × 3″

3″ × 3″ kiss-cut sticker.

Shipping

Flat $6 shipping on every order, worldwide, whatever's in it.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Meet Effio, a light bulb who turns some of his energy into light and loses the rest as heat.

Energy is never destroyed, but it does not always go where we want. Efficiency compares the useful energy a device puts out with the total energy put in, η = E_out/E_in. It is usually written as a percentage and can never be more than 100%.

Suppose a bulb takes in 60 J of electrical energy and gives out 6 J as visible light. Its efficiency is 6 / 60 = 0.10, or 10%. The other 54 J is not lost from the universe. It warms the bulb and the room around it.

Efficiency can be raised by cutting waste, for example with less friction, better insulation or a different technology, but the total energy always balances.

For heat engines there is an extra limit, the Carnot efficiency, which depends only on the hot and cold temperatures. Even a perfect engine cannot turn all of its heat into work.

Equations

\[\eta = \frac{E_{\text{out}}}{E_{\text{in}}}\]
SymbolMeaningUnit
\(\eta\) efficiency \(\mathrm{no unit}\)
\(E_\text{out}\) useful energy output \(\mathrm{J}\)
\(E_\text{in}\) total energy input \(\mathrm{J}\)

Sources

  1. OpenStax College Physics 2e — Conservation of Energy
  2. OpenStax University Physics Vol. 2 — Heat Engines

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