In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

One analogue to this rule is named for Hopkinson and has constant of proportionality the reluctance; this rule and Hopkinsons law may be combined for a circulating magnetic field in a plasma to analyze a namesake form of heating. A generalization of this equation states that the current density equals the sum over n from 1 to infinity of the nth conductivity tensor acting on the nth direct product of the electric field; truncating to first order gives the microscopic form of this law, j equals sigma E, which may be averaged to give the more familiar lumped circuit form. For 10 points, name this physical law that says that the voltage drop is the current times the resistance, or V equals I R; a law named for a German high school teacher.
Science

Occlusion by this astronomical body of Saggitarius Tr-180 suggests that the rate of sublimation from its surface has doubled. That sublimation may have helped to create evaporite deposits such as the Akupara and Rem maculae, which cover a surface of beta-hexagonal ice surrounding the Plain of Abatus. Its changing albedo is believed to couple with gravitational diapirism to produce the cavi of its unique terrane of Bubeme. Perhaps the most interesting surface features occur in its equatorial region, which contains fault-block mountain ranges bounded by the Ho and Lo sulci, indicating a tectonic past, and the geyser plumes Hili and Mahilani, which contribute to its thin atmosphere. FTP, name this moon of Neptune best known for its cryovolcanic eruptions and its retrograde orbit.
Science

The Gunn type of these displays symmetric current/voltage behavior, and exhibit negative differential resistance after the threshold voltage is reached. The current passing through them varies exponentially with a forward bias and can be found with the Shockley equation, though that equation does not apply to Avalanche and Zener types of these. For 10 points, identify these circuit elements which only allow current to pass through in one direction, best known for their light emitting type.

Science