The heliocentric model of the solar system was proposed by
Answer: A
Copernicus proposed it.
De Revolutionibus Orbium Coelestium, published in 1543 as he lay dying, placed the sun rather than the earth at the centre. Galileo's telescopic observations later supplied the evidence, at considerable cost to himself.
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Gun powder was invented in 9th century in
Answer: B
It was invented in Tang dynasty China.
Alchemists searching for an elixir of immortality recorded in the ninth century that saltpetre, sulphur and charcoal burned fiercely together, warning that it could singe beards and burn down houses. It was used in warfare from the Song period.
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First solar cell was invented in 1883 by
Answer: D
Charles Fritts made it.
He built the first solar cell in 1883 by coating selenium with a very thin layer of gold. Its efficiency was under one per cent, but it showed that light could be converted directly into electricity without heat or moving parts.
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In about which year was the printing press with movable type invented in Europe?
Answer: D
It was about 1440.
Johannes Gutenberg developed movable metal type, an oil-based ink and a press adapted from the wine press at Mainz in the 1440s, and printed his Bible about 1455. Movable type had existed earlier in China and Korea, but Gutenberg's system suited an alphabet and spread rapidly.
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Scientists who have provided basis for inventing Circuit Breaker are
Answer: C
Both Joseph Henry and Michael Faraday.
Their independent discovery of electromagnetic induction in the early 1830s underlies the circuit breaker, which senses excess current through a coil and uses the magnetic force it generates to trip the contacts.
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The QWERTY layout used on typewriters and computer keyboards was devised by
Answer: A
Christopher Sholes devised it.
He arranged the keys of his 1873 typewriter so that letters often typed in succession sat far apart on the typebar basket, which stopped the bars from jamming. The layout survived the mechanism it was designed for.
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Earth inductor compass is
Answer: C
It is an American invention.
Morris Titterington devised the earth inductor compass in the 1920s. It measures the current induced by the earth's magnetic field in a rotating coil, and being unaffected by the aircraft's motion it was far steadier than a magnetic compass. Lindbergh used one to cross the Atlantic.
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Vulcanized rubber was invented by
Answer: B
Charles Goodyear invented it.
He found in 1839, by dropping a mixture of rubber and sulphur on a hot stove, that the result stayed elastic in heat and cold alike. He spent his life in debt over it and died owing $200,000.
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The first practical direct-current electric motor was invented by
Answer: B
Frank Julian Sprague built it.
His constant-speed DC motor of 1886 held its speed under varying load, which earlier motors could not, and made electric traction practical. He equipped the Richmond streetcar system in 1888, the first successful electric tramway.
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Nuclear power was used for first time to produce electricity in
Answer: D
It was 1951.
Experimental Breeder Reactor I in Idaho lit four light bulbs on 20 December 1951 - the first electricity generated from nuclear energy. The first station to supply a grid was Obninsk in the Soviet Union in 1954.
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