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In 1886, Frank Julian Sprague invented the first practical DC motor, a non-sparking motor that maintained relatively constant speed under variable loads. Other Sprague electric inventions about this time greatly improved grid electric distribution (prior work done while employed by Thomas Edison), allowed power from electric motors to be returned to the electric grid, provided for electric distribution to trolleys via overhead wires and the trolley pole, and provided controls systems for electric operations. This allowed Sprague to use electric motors to invent the first electric trolley system in 188788 in Richmond VA, the electric elevator and control system in 1892, and the electric subway with independently powered centrally controlled cars, which were first installed in 1892 in Chicago by the South Side Elevated Railway where it became popularly known as the "L". Sprague's motor and related inventions led to an explosion of interest and use in electric motors for industry, while almost simultaneously another great inventor was developing its primary competitor, which would become much more widespread. The development of electric motors of acceptable efficiency was delayed for several decades by failure to recognize the extreme importance of a relatively small air gap between rotor and stator. Efficient designs have a comparatively small air gap. [a] The St. Louis motor, long used in classrooms to illustrate motor principles, is extremely inefficient for the same reason, as well as appearing nothing like a modern motor.
Who did Sprague work for early in his career?
A: Thomas Edison

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The reemergence of Cubism coincided with the appearance from about 191724 of a coherent body of theoretical writing by Pierre Reverdy, Maurice Raynal and Daniel-Henry Kahnweiler and, among the artists, by Gris, Leger and Gleizes. The occasional return to classicismfigurative work either exclusively or alongside Cubist workexperienced by many artists during this period (called Neoclassicism) has been linked to the tendency to evade the realities of the war and also to the cultural dominance of a classical or Latin image of France during and immediately following the war. Cubism after 1918 can be seen as part of a wide ideological shift towards conservatism in both French society and culture. Yet, Cubism itself remained evolutionary both within the oeuvre of individual artists, such as Gris and Metzinger, and across the work of artists as different from each other as Braque, Leger and Gleizes. Cubism as a publicly debated movement became relatively unified and open to definition. Its theoretical purity made it a gauge against which such diverse tendencies as Realism or Naturalism, Dada, Surrealism and abstraction could be compared.
Name the three writers who were in part resonsible for the reemergence of Cubism between 1917 and 1924.
A: Pierre Reverdy, Maurice Raynal and Daniel-Henry Kahnweiler

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The concentration of copper in ores averages only 0.6%, and most commercial ores are sulfides, especially chalcopyrite (CuFeS2) and to a lesser extent chalcocite (Cu2S). These minerals are concentrated from crushed ores to the level of 1015% copper by froth flotation or bioleaching. Heating this material with silica in flash smelting removes much of the iron as slag. The process exploits the greater ease of converting iron sulfides into its oxides, which in turn react with the silica to form the silicate slag, which floats on top of the heated mass. The resulting copper matte consisting of Cu2S is then roasted to convert all sulfides into oxides:
What do the sulfides convert to after the copper matte is roasted?
A: oxides

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The United Kingdom has traditionally been governed as a unitary state by the Westminster Parliament in London. Instead of adopting a federal model, the UK has relied on gradual devolution to decentralise political power. Devolution in the UK began with the Government of Ireland Act 1914 which granted home rule to Ireland as a constituent country of the former United Kingdom of Great Britain and Ireland. Following the partition of Ireland in 1921 which saw the creation of the sovereign Irish Free State (which eventually evolved into the modern day Republic of Ireland), Northern Ireland retained its devolved government through the Parliament of Northern Ireland, the only part of the UK to have such a body at this time. This body was suspended in 1972 and Northern Ireland was governed by direct rule during the period of conflict known as The Troubles.
When did revolution in the UK begin?
A:
unanswerable