• Elastrix – Gough–Joule Effect physics T-shirt
  • Elastrix – Gough–Joule Effect physics T-shirt
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ElastrixGough–Joule Effect (Entropic Elasticity)

Elastrix – Gough–Joule Effect (Entropic Elasticity) Physics T-Shirt

$29.99 USD
$29.99 USD
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Color
White · Black
Size
S–5XL
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Why does heated rubber pull harder? A stretched rubber band’s chains are partly straightened, and thermal motion keeps pushing them back toward tangled, higher-entropy shapes. Heat it and that pull grows, so the band contracts and can lift a weight. John Gough noticed the effect, and James Joule measured it carefully in 1859. Pixel-art unisex tee; equation, symbols and sources in the physics panel below.

Color
Size

Size guideS–5XL · inches

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

Measurements in inches, ±1.5 in tolerance.

ShippingFree US

Free US shipping · $10 flat shipping outside the US. Printed to order for you.

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

Hang a weight on a rubber band and heat the band. It shrinks and lifts the weight. Most materials expand when heated; stretched rubber pulls tighter.

John Gough noticed it in 1805 and James Joule measured it in 1859. Rubber is a tangle of long chains. Stretching lines them up and lowers their entropy, so the pull is almost entirely entropic, and it grows in proportion to temperature.

Heat Elastrix. She tightens.

Equations

\[f = \left(\frac{\partial U}{\partial L}\right)_T - T\left(\frac{\partial S}{\partial L}\right)_T \;\approx\; -T\left(\frac{\partial S}{\partial L}\right)_T\]
\[\left(\frac{\partial f}{\partial T}\right)_L = -\left(\frac{\partial S}{\partial L}\right)_T > 0\]
SymbolMeaningUnit
\(f\) tension in the rubber band \(\mathrm{N}\)
\(U\) internal energy \(\mathrm{J}\)
\(S\) entropy \(\mathrm{J/K}\)
\(L\) length of the band \(\mathrm{m}\)
\(T\) absolute temperature \(\mathrm{K}\)

Sources

  1. Joule (1859) On some thermo-dynamic properties of solids, Phil. Trans. R. Soc. Lond. 149, 91
  2. Feynman Lectures on Physics Vol. I Ch. 44: The Laws of Thermodynamics (rubber band)
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