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Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

Why is DC motor being used more than AC type?
Answer: conversion was not well developed
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Copper is synthesized in massive stars and is present in the Earth's crust at a concentration of about 50 parts per million (ppm), where it occurs as native copper or in minerals such as the copper sulfides chalcopyrite and chalcocite, the copper carbonates azurite and malachite, and the copper(I) oxide mineral cuprite. The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the largest described single crystal measuring 4.43.23.2 cm.

What year was the largest find of copper discovered?
Answer: 1857
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A microbrewery, or craft brewery, produces a limited amount of beer. The maximum amount of beer a brewery can produce and still be classed as a microbrewery varies by region and by authority, though is usually around 15,000 barrels (1.8 megalitres, 396 thousand imperial gallons or 475 thousand US gallons) a year. A brewpub is a type of microbrewery that incorporates a pub or other eating establishment. The highest density of breweries in the world, most of them microbreweries, exists in the German Region of Franconia, especially in the district of Upper Franconia, which has about 200 breweries. The Benedictine Weihenstephan Brewery in Bavaria, Germany, can trace its roots to the year 768, as a document from that year refers to a hop garden in the area paying a tithe to the monastery. The brewery was licensed by the City of Freising in 1040, and therefore is the oldest working brewery in the world.

What year was The Benedictine Weihenstephan Brewery first licensed as a brewery?
Answer:
1040