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11oz · 15oz
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Why does a thin wire get hot? Ohmbert resists. Ohm’s law, V = IR, says the current through a conductor is proportional to the voltage across it, with resistance setting the ratio. More resistance means less current for the same voltage, and energy lost as heat. Pixel-art black ceramic mug in 11 or 15 oz; equation, symbols and sources in the physics panel below.

Size

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.

ShippingFree US

Free US shipping. $10 flat shipping outside the US.

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

Ohmbert stands in the wire and makes the current earn every step.

By 1827 Georg Simon Ohm had established that, for many materials at fixed temperature, the current through a conductor is proportional to the voltage across it. The ratio is the resistance. Triple the voltage, triple the current; that is the first line.

YOU SHALL NOT PASS. EASILY. More resistance means less current for the same voltage. And the current that does pass loses energy along the way. The second line gives the power turned into heat. A thin wire has more resistance than a thick one of the same metal, so at the same current it heats more, which is how toasters and old light bulbs work.

Ohm's law is a rule for ohmic materials such as metals at steady temperature. Diodes, transistors and glowing filaments, whose resistance changes with current or temperature, do not follow a single straight line.

Ohmbert lets you through. He just takes a cut.

Equations

\[V = I\,R\]
\[P = I^{2}R\]
Symbols
SymbolMeaningUnit
\(V\) voltage (potential difference) across the conductor \(\mathrm{V}\)
\(I\) current through it \(\mathrm{A}\)
\(R\) resistance \(\mathrm{Ω}\)
\(P\) power turned into heat in the resistance \(\mathrm{W}\)
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