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USES OF NOBLE CASES

Helium Since helium is lighter than air and is not flammable,

it is used instead of hydrogen to inflate zeppelins, hovercrafts,

and weather balloons. It is used in magnesium welding to prevent

oxidation of magnesium. In order to produce artificial atmosphere

for divers and tunnel builders, it is used by mixing with oxygen and

neon. Helium is used in mercury vapor lamps. In rocket fuel, it is used

to keep pressure constant as the fuel is used up. In nuclear reactors,

helium is used to cool the core.

If we cool metals down to very low temperatures, they lose their

electrical resistance. They become perfect conductors,

or super-conductors.Liquid helium is used to cool metals down.

It boils at -269°C!

It is used to cool the coils in body scanners.

The coils can then make the very strong magnetic fields that

scanners require.

Neon is used in welding more widely than helium.

It is used in helium-neon lasers. It is also used in

advertisement signs called neon lights.

Argon is used in electric lamps. The gases Ar-N2

are to fill react tungsten lamps. Because Ar gas does not

react with tungsten, it prevents the oxidation of this metal.

Argon and Hg are used in fluorescent lamps.

It is also used in welding. It acts as a shield around the weld.

The argon stops the hot metal from reacting with oxygen in the air.

Krypton and xenon are used for taking photographs rapidly. The light obtained by passing current through Xe-Ne gases is the most suitable for taking photographs. This light is five times better than the light obtained from Fleming lamps. If current is passed through Xe, a very dense white light can be obtained. Today, krypton is used in lasers to repair the retina behind the eye.

UNIT-3

Читайте також:

1. Grammatical Categories. The Use of Cases
2. II. Listen again. Choose the right option to complete the following sentences. In some cases more than one option is possible
3. IV. Choose the correct option. In some cases more than one answer is possible
4. Scan passage 2. Pay attention to the requirements to abstracts and papers sent to a conference. Say if it’s sometimes possible to exceed the limit? In what cases can it be done?
5. What prosodic means are used in different cases of accent in the text?
6. What prosodic means are used in different cases of accent in the text?

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