Прочитайте текст. Lead is now a very expensive metal. At one time it was used extensively for roofin...: ответ на тест 857122 - Английский язык

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What is lead monoxide used for?
Lead is now a very expensive metal. At one time it was used extensively for roofing and for water piping because of its softness and resistance to corrosion. But later copper and iron have taken its place. Lead is a grey malleable metal which melts at 327 ̊C, which is low for a metal. Lead is still used for roofing and for making waste pipes and sink traps because it is easily bent into shape; storage battery (accumulator) plates; storage tanks for sulphuric acid; lead shot; solder; screens to stop harmful radiation from radioactive substances. Lead monoxide is used for making glass that is brilliant and sparkling, i.e. decorative tableware.

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We use metals for a variety of engineering purposes. Some metals have ductile properties. If a metal is ductile, it can be pressed into a new shape. Copper is an example of this. It is a ductile metal because it can be stretched into another shape. Lead can be also pressed into a new shape.
Copper is a good conductor of electricity. We often use it for electrical conductors. And lead can be used for electrical cables because it resists corrosion.
Cast iron is unlike copper and lead. Its shape cannot be altered and it is not able to resist corrosion.
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What kind of conductor is copper?

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Iodine, a steel-gray solid, readily vaporizes when heated. The vapor is violet in colour. If the vapor is allowed to cool, it passes directly back into the solid state. This process of passing from the solid state to the vapor state and then back to the solid state without the formation of a liquid is called sublimation. If a saturated solution of potassium nitrate is heated and then allowed to cool, crystals of the substance form on the bottom of the vessel. These are formed by precipitation, which takes place during the cooling process.
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Iodine readily vaporizes …

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The television receiver includes tube circuits for receiving, amplifying, and synchronizing the signals, and a large cathod tube called a kinescope. This part of the device converts the video impulses from the transmitting station into luminous spots on a fluorescent screen. In the kinescope the amplified video signals are applied to the grid, and through it control the intensity of the electron beam.

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In the colour receiver the incoming signal goes through frequency and amplitude selective circuits. In these circuits the brightness components, the colour components, and the horizontal and vertical beam-synchronizing components are separated. The brightness component is applied simultaneously to each of the three electron guns. The red, green, and blue colour signal voltage components are produced and are applied to the three respective kinescope electron guns. They combine with the brightness components voltage to produce beam intensities which reproduce the original picture.

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Telephony is the branch of telecommunication which provides for the exchange of information in the form of speech. In any telephone system speech or other sounds are converted into electric signals that are transmitted to a distant point where they are converted back into reproductions of the original sound.
Telephone set is an assembly of apparatus provided at each end of a telephone circuits to enable the user to make and receive calls.
A microphone forming part of a telephone set is called a telephone transmitter while a transducer forming part of a telephone set and used to convert voice-frequency currents into audible sounds is telephone receiver. The system also includes an electric bell responsive to low-frequency AC or pulsating current and is used as a calling device at a telephone station.