The Cold Circuit: Tesla's 1901 Patent for Chilling Electrical Circuits (U.S. 685,012)
In short: U.S. Patent No. 685,012, Means for Increasing the Intensity of Electrical Oscillations, was granted to Nikola Tesla in 1901. It proposes cooling a circuit's conductors to very low temperatures, for example with liquid air, so that their electrical resistance drops and oscillations in the circuit can build up far more strongly.
What problem was Tesla solving?
Every electrical circuit loses energy as heat because of resistance in its wires. In an oscillating circuit, those losses damp the oscillations, limiting how strong they can become. For Tesla's high-voltage experiments, every bit of lost energy mattered.
Why cold?
The resistance of metals falls as they get colder. Tesla's patent applies that principle directly: surround the conductors with a cooling agent such as liquid air, and the circuit wastes less of its energy, so the oscillations can grow more intense.
Why does it matter today?
The patent arrived in 1901, about ten years before Heike Kamerlingh Onnes discovered superconductivity in 1911, the phenomenon in which some materials lose all electrical resistance at extremely low temperatures. Tesla wasn't describing superconductivity, but he was pointing in the same direction: cold as a tool for better electrical performance.
What does the drawing show?
The drawing shows a coil arrangement with its cooling setup. It's one of the wider, more horizontal designs in the collection.
Read more from the Archive
Wear the drawing: The Cold Circuit — N. Tesla, 1901, part of XVI — The Tower.