English: Drawing illustrating the operation of a hypothetical passive negative static resistance. An ordinary positive static resistor (illustrated in the companion drawing Thermodynamics and positive resistance.svg) dissipates electric power supplied to it, converting it to heat, which warms the surrounding environment. A hypothetical passive negative static resistance, shown here, which works like a positive resistor in reverse, would absorb heat from the surrounding environment, cooling it, and convert the heat into electric power which would be consumed in the attached circuit. However this is prohibited by the second law of thermodynamics, which says it is impossible for a machine to convert heat from a single temperature reservoir to work, a temperature difference is required. Therefore a negative static resistance cannot be a passive device, it must be an active device, with a source of energy.