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Galileo
Galileo

Galileo. Galileo Galilei Galileo Galilei
(1564 - 1642). An Italian scientist who was one of the first to move away from the ideas of Aristotle and others descended from antiquity. He was the first to use a telescope in his research. His ideas about the dynamics and structure of the universe led to many disputes.


galvanometer
Galvanomètre

Galvanometer. The Italian scientist Galvani was the first to reveal the existence of small currents through his well-known experiment on the legs of a frog. Therefore, the sensitive meter designed specifically to measure small currents was called a galvanic meter. Today this scale is called the milliampere scale.
See ammeter.


gamma radiation (y)
radiation f gamma

Gamma radiation produces high-energy electromagnetic waves with short wavelengths during the decay of certain nuclei. See radioactivity. The energy leaves as a “packet,” quantum, or photon of radiation. The nucleus does not change its structure, but it becomes more stable.

Gamma radiation can pass through matter easily and slowly lose energy by forming ions. See radiation detector. Due to its wide range, it may cause profound harm to the body, and workers who deal with materials that emit this radiation must protect themselves with a lead or cement shield.


gas. gas
gaz m

Gas. The natural state of matter whose particles carry the highest energy. These particles move at speeds of up to hundreds of meters per second and fill all the space available to them. The density of a gas is much lower (about 1000 times) than the density of any solid or liquid. Gases result from the evaporation of solid and liquid bodies, the sublimation of solid bodies, and the boiling of those liquids.

Gas differs from vapor in that it is not transformed into a liquid merely by pressure.
See circular temperature.


gas laws
Lois fpl des gas

Gas laws. These laws determine the pressure (P pressure), volume (V volume), and absolute temperature (T) of gas samples. There are three laws, each of which relates to a fixed mass of gas.

Boyle's law: For a fixed mass of gas at a fixed temperature, the pressure multiplied by the volume is constant.

Charle's law: For a fixed mass of gas subjected to constant pressure, the volume is directly proportional to the absolute temperature.

Pressure law: For a fixed mass of gas with a fixed volume, the pressure is directly proportional to the absolute temperature.

For some reason, the gas sample moves from one state, T1, V1, p1, to another, T1, V1, p2. Thus, we can write the three laws as follows:

Boyle P1V1 = V2P2

Charles V1/T1 = V2/ T2

Pressure P1/T1 = P2/T2

The three laws combine in the ideal gas equation, which applies to samples of fixed mass:

P1V1/T1 = P2V2/T2

All of these statements apply to ideal gases only. In practice, real gases follow these laws at normal temperatures and pressures.


gate
circuit m logique

Gate . See logic gate.

gear. gear
engrenage m


serrated. Interlock. A toothed wheel whose task is to transfer torque or rotational movement from one drive shaft to another drive shaft. The interlock system is a type of machine. The torque ratio (compare with the force ratio) is equal to the gear ratio, that is, the ratio of the number of gear teeth at the input wheels and the output wheels.

The two drawings below show the simplest gearing system: “The cylindrical spur gear (A) is used to change the torque or rotational speed between two parallel drive shafts. In Figure (B), the output drive shaft rotates in the same way as the input drive shaft.

To reduce slippage, the teeth are on the right side
The process is much more complex than shown.