A point of some confusion is whether ordinary resistance ("static" or "absolute" resistance, R static = v / i ) can be negative. In electronics, the term "resistance" is customarily applied only to passive materials and components – such as wires, resistors and diodes. These cannot have R static < 0 as shown by Joule's law P = i 2 R static . A passive device consumes electric power, so from the passive sign convention P ≥ ≥ 0 . Therefore, from Joule's law R static ≥ ≥ 0 . In other words, no material can conduct electric current better than a "perfect" conductor with zero resistance. For a passive device to have R static = v / i < 0 would violate either conservation of energy or the second law of thermodynamics, (diagram). Therefore, some authors state that static resistance can never be negative.