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Coulombo

Coulomb’s Law Physics

\[F = k_e\,\frac{q_1 q_2}{r^{2}}\]
$21.99 USD
$21.99 USD
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Why do opposite charges cling together? Coulombo feels the pull. Coulomb’s law, F = keq1q2/r², says the electric force between two point charges grows with their product and falls with the square of the distance. Like charges repel; opposites attract. Pixel-art black ceramic mug in 11 or 15 oz; equation, symbols and sources in the physics panel below.

Shipping calculated at checkout by destinationMade to order, ships in ~10 days

Details

Size & material11oz · 15oz

Black glossy ceramic mug with a C-handle. Lead- and BPA-free.

  • 11oz: 0.33 l
  • 15oz: 0.44 l
CareDishwasher & microwave safe

Dishwasher safe (top rack) or hand wash. Microwave safe.

ShippingBy destination

Shipping calculated at checkout by destination.

Made to order: about 10 days of production and handling before it ships.

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

Two charges push or pull on each other with a force proportional to the product of the charges and inversely proportional to the square of their distance. Like charges repel and opposite charges attract.

Coulombo is charged, and he has a type.

Charles-Augustin de Coulomb established in the 1780s the law on this mug. The electric force between two point charges grows with the product of the charges and falls off with the square of the distance between them, just like Newton's gravity. Unlike gravity, it comes with a sign. Like charges repel; opposite charges attract. OPPOSITES ATTRACT. LITERALLY.

It is also enormously strong. Two charges of one coulomb each, a metre apart, would push on each other with about nine billion newtons. Ordinary matter hides this because it is almost perfectly neutral: positive and negative charges cancel to extraordinary precision.

Atoms hold together by this force, electrons bound to nuclei. Chemistry, friction, the stiffness of a table and the grip of your hand are all electric forces at bottom.

Coulombo does not need to be close to feel it. He just feels it more.

Equations

\[F = k_e\,\frac{q_1 q_2}{r^{2}}\]
\[k_e = \frac{1}{4\pi\varepsilon_0}\]
\[k_e \approx 8.99\times10^{9}\ \text{N m}^{2}\,\text{C}^{-2}\]
SymbolMeaningUnit
\(F\) electric force between two point charges (positive: repulsion, negative: attraction) \(\mathrm{N}\)
\(k_e\) Coulomb constant \(\mathrm{N·m²/C²}\)
\(q_1, q_2\) the two charges, with sign \(\mathrm{C}\)
\(r\) distance between the charges \(\mathrm{m}\)
\(\varepsilon_0\) vacuum permittivity \(\mathrm{F/m}\)

Sources

  1. HyperPhysics — Coulomb's Law
  2. Encyclopaedia Britannica — Coulomb’s law
  3. Feynman Lectures on Physics Vol. II Ch. 4: Electrostatics
  4. NIST CODATA 2022 — vacuum electric permittivity

Source Coulomb, C.-A. (1785). Premier mémoire sur l’électricité et le magnétisme. Histoire de l’Académie Royale des Sciences (année 1785), 569–577.

Field notes

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