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Does an electric fan lower the temperature of a room?

June 3, 2017 | Author: | Posted in Science

An electric fan running in a perfectly insulated and hermetically sealed room would not make the air in the room cooler, as commonly supposed. In fact, because of the friction developed in the fan, the temperature of a room is slightly increased instead of decreased by setting the air in rapid motion. The cooling effect of the fan results …

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Can stars be seen in daytime from a well?

June 1, 2017 | Author: | Posted in Science

The popular belief that stars and planets can be seen in the daytime from the bottom of a well or shaft is true only to a very limited extent. A person observing the stars in daylight is assisted by a shaft or tube in two ways. The pupil of the eye is protected from stray light and lateral illumination. …

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What is the belief about the seventh son of a seventh son?

May 30, 2017 | Author: | Posted in Science

It was once widely believed that the seventh son of a seventh son (or child or either sex as some supposed) was endowed with notable talent and supernatural powers. According to a belief that persisted through the Middle Ages, the seventh son of a seventh son is endowed with the power not only of curing diseases and disorders of …

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Is quicksilver mined?

May 17, 2017 | Author: | Posted in Science

Quicksilver is the popular name of mercury, a heavy silver-white element. It is unique among the metallic elements in that it remains liquid at ordinary temperatures. Mercury occurs in nature in a free state, both in lodes and placer deposits, but only in small quantities. Commercial mercury is obtained chiefly from cinnabar ore, the sulphide …

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Does odor have weight?

April 15, 2017 | Author: | Posted in Science

Odor is the name of the sensation produced when certain substances come in contact with the olfactory region. The term is also applied to the collective diminutive particles that produce this sensation. Very little is known about the sense of smell and it is a disputed question whether it depends on a chemical or physical …

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Is it easier to lift a weight with a large or small pulley?

March 15, 2017 | Author: | Posted in Science

Other things being equal, a weight can be lifted more easily with a large pulley than with a small one. Less power is required to drive or pull a vehicle with large wheels than is required to drive or pull one with small wheels. The larger the wheel, the greater the mechanical advantage in overcoming …

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What is the lightest substance known?

March 11, 2017 | Author: | Posted in Science

The element hydrogen is the lightest substance known to science. Its specific gravity, compared to air, is 0.0695. Helium, with a specific gravity of 0.139, is the next lightest substance. Specific gravity is relative density, that is, the ratio of the weight of any volume of a substance to the weight of an equal volume …

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Does air have weight?

March 10, 2017 | Author: | Posted in Science

Air is a substance and all substances have weight. Air, however, is very light. A column of air an inch square extending from sea level upward as far as the atmosphere goes weighs only about fifteen pounds. This is called atmospheric pressure. Galileo first demonstrated that air has weight by weighing a glass globe, then …

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What is spontaneous combustion?

February 18, 2017 | Author: | Posted in Science

Spontaneous combustion is the ignition of a combustible material without the application of external heat or flame. The self-generated heat produced by cotton soaked in oil and confined in a poorly ventilated room sometimes becomes sufficient to ignite the cotton. Fires started by spontaneous combustion are common in coal mines, owing chiefly to the rapid oxidation …

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Is steam visible?

January 3, 2017 | Author: | Posted in Science

Strictly speaking, steam is invisible. The term is properly applied to the transparent gas or vapor into which water is converted when heated to the boiling point. The visible mist commonly called steam, which consists of minute droplets of water in the air, is not formed until the water vapor has cooled and condensed.

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