Text 5 b Scales of Temperature

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Temperature is usually measured on either the centigrade or Fahrenheit scale. In scientific work the centigrade system is used exclusively, but in engineering the Fahrenheit scale is preferred in many countries. This has led to much confusion, but difficulties can be avoided if one remembers that the fixed points on both scales are the melting point of ice and the boiling point of water. The height to which the thread of the liquid rises in a thermometer of the usual construction when immersed in an ice-water mush is marked as 0° on the centigrade scale or 32° on the Fahrenheit. A similar mark is made when the thermometer is placed in steam above boiling water; this becomes 100° centigrade or 212° Fahrenheit. The distance between these fixed points is divided into equal intervals thus making 100 divisions on the centigrade scale equivalent to 180 divisions on the Fahrenheit. The Fahrenheit division is smaller than the centigrade division in ratio 5:9.

Since there are two scales in common use, the problem often arises of converting readings on one scale to the other. Let us consider a practical example. We wish to convert 95° F to centigrade. This is 95-32=63 degrees above the melting point of ice on Fahrenheit scale. Hence the distance AB is 63 degrees on the Fahrenheit scale or equivalent to 5/9 of 63=35 degrees on the centigrade scale. Therefore the temperature is 35° C. Suppose that it has been required to convert 35° C to Fahrenheit. We would reason as follows: From A to B is 35-centigrade divisions or 9/5 of 35=63 divisions on the Fahrenheit scale. These divisions added to 32 (since the Fahrenheit reading is 32 when the centigrade is zero) make the actual reading 95° F.

Unit 6 Grammar:

1. Modal verbs.

2. Nouns as attributes.

Reading exercises

I. Practise reading the following one-syllable words:

fact, back, hand, land; range, made, same, face, safe, take, name, wave; large, star; clock, fog, strong; both, whole; storm, short, word; set, get; these, three; beam; pick, ship, this, give, which; wide, blind, time, life, strike; fly; high, night, light; pulse, just, thus; use.

II. Practise reading two-syllable words with the stress on the first syllable:

radar, ranging, harbour, landing, travel, measure, beacon, presence, weather, echo, signal, timer, system, object, constant, mountain, strongest, portion, during.

III. Practise reading two-syllable words with the stress on the second syllable

across, appear, equip, complete, desired, direct, consist, entire, present, install, reflect, rotate, translate, within.

IV. Practise reading the following many-syllable words:

determination, equipment, capable, direction, character, recognize, essential, component, transmitter, receiver, antenna, indicator, frequency, fluorescent, interval, predetermined, synchronizer, velocity, accuracy, azimuth, elevation.

V. Practise reading the following word combinations:

capable of determining, the presence of objects, their character, all of them, ultra-high frequency radio wave energy, directional antenna, in a beam, visual readable signals, within the field of view of radar, the use of these timed pulses, at the constant velocity, the fluorescent screen, predetermined interval, the accuracy of the range, with the help of a radar set, location of an object, entirely safe, regardless of night or weather, to fly over mountain ranges.