INGLESE TECNICO -CONDUCTORS AND INSULATOR

In electrical work a conductor is defined as a material which allows the free passage of an electric current along it, while  the term insulator  indicates a material which offers an extremely  high resistance  to the passage of an electric  current
There is no such thing as a perfect insulator for all substance conduct electricity to a Greater o lesser extent, but the difference in resistivity  between  conductors and insulator  is so enormous that there is no possible ambiguity in this classification
Thus slate , which  is a relatively poor insulator has nevertheless a resistivity  10/12 times higher than a high-resistance  alloy, which is a bad conductor  while the ratio between the resistivity  of the worst and best  conductors is much smaller
the resistivity of nichrome for istance is about seventy times the of copper
those materials which fall in between conductor and insulator  are classed as semi-conductors (germanium
The resistivity of any material is a constant for any specified temperature m but  varies with this 
The resistance of copper and most othe r conductor  increases with temperature
the resistance of  constantan and other usful alloy  is pratically constant within wid limits of temperature  while resistance of carbon of electrolytes and  of most  dielectrics decreases as  the  temperature rises
Because of this decrease in resistance which occurs in insulating materials a limit in the rise in temperature is imposed in their applications, otherwise the insulation would break down to cause a leakage current or even a short circuit
conductor and insulators  used in electrical work are extremely  veried and of a most diverse nature 
Because no single material can be used too extensively both for costs and availability  different materials are usually combined  to fhve the required  properties  of mechanical strength adaptability and  reliability

INGLESE - ESERCIZI SULL'INGLESE TECNICO

read these sentences through then replace  quality and  characteristic  y property or grade

1.  materials are accurately tested so that their electrical characteristics can be  assesse and compared

2. the oxid film which forms on alluminium increas its corrosion-resisting  qualities

3. the body  of a high breaking capacity  cartridge  fuse  is  of high-qualitiy  ceramic

4. the most important  quality of copper is  its high electrical conductivity  

5.in the early 20th  century it was discovered that electron emission  from heated metals  is a true quality of the metals  themselves  and is not  a secondary  effect due to the presence  of gas

6. paper thugh higly hygrospocpic is used as  an insulator in many applications on account of its  flexibility and good electric qualities

7. welded-seam conduit  is used for most commercial quality  installation  work

8. the magnetic qualities  of iron  and cerain special iron alloys are essential to commercial electrical  machine and trasformers

9. the quality  of this uranium ore is too low  for economic working

10. it is  seldom possible  to obtai in one material the ideal mechanical and electrical  characteristics

INGLESE TECNICO - SUITABILITY

the large scape application of electrical energy requires new materials  to  suit
                                                                                                                       serve   specific purposes
                                                                                                                       fulfill

many forms of potentiometers are on the market  to  suit
                                                                                     meet
                                                                                     answer  the needs of classes of testing work
                                                                                     satisfy

some cables  are designed with  a view to cheapness and    are particularly suited to  domestic
                                                                                              suit very well                   installation

suitable
appropriate   magnetic properties con be obtained by  means  of the    right
                                                                                                                correct    heat treatment
                                                                                                                proper

electrostatic instruments are a     suitable       means for measuring continuous o alternating voltages
                                                     convenient

new power station  were installed in the  appropriate
                                                                  right                  area  so as to answer  the needs of the      
                                                                                            country

mercury switches are       suitable
                                         fit                      only for weak currents and low voltages

adequate          mechanical strength  is a primary requirement of any  electrical connection
sufficient

vocabulary

potentiometers = potenziometro
testing work = prove, misure
heat treatmente = trattamento termico
continuous or alternating voltages  tensioni continue e alternate
mercury switch  = interruttore a mercurio

INGLESE TECNICO - QUALITY GRADE PROPERTY

quality  =  grade  (degree of excellence )
                  property (distinctive caracter)

strength
hardness                                             qualities
ductility                               are          properties           of metals
electrical conducitivity                       characteristics
resistance  to corrosion


High resistance                                     qualities
dielectric strength                        are    properties              of insulators
heat dissipation capacity                       characteristics
resistance to chemical factors


viscosity
volatility                                         qualities
specific heat                          are   properties                          of insulating oils
Thermal conductivity                    characteristics
density

copper is a high  -                                                              conductive  material
insulating  materials  of a commercial     quality                offer less resistance to wear    
magnetic materials  of a suitable              grade              are essential in the construction of   
                                                                                           electromagnetic devices          

INGLESE TECNICO

MATERIALS USED IN ELECTRICAL ENGINEERING

INTRODUCTION

over the last half century  the use of electrical energy ha enourmously increased for virtually all domestic and industrial purpose
this fact is a proof that the electrical industry plays a most prominent part in the economy  of a country and in the history of its social progress
The large-scale  application of electrical energy has required an enormous investment in resources both  economic and human in many branches  of science
In connection with all other  problems however it is  the research on the materials  which  has alwuys been given special attention
Som materials have been selected  either for their electrical  and mechanical characteristics or for their  commercial availability
In order to improve properties suitable  for specific purposes Others have become object of research in laboratories financede from contributions of private  firms, often with adequate  assistance  from the state
Finally  it has been necessary  to find new materials  answering the requirements implied  by the develpmente of the electrical industry
Electrical materials can be classified in any number of Group according to their  main purposes and to their properties in individual applications
For general purposes they are  classified in five main Group  : conductors, insulators , semi-conductors, magnetic materials and refractories
Some materials  however may  serve hìother purposes besides those directly  related to  their main property
Iron for instance  is a magnetic material but is also used for constructional purposes  and with other elements in the form of a ferrous  alloy it is resistive condictor  as found in heating  elements

vocabulary
to finance = finanziare
refractory = refrattario
alloy = lega
resistive conductor = conduttore resistivo

guide to summery (riassunto )

answer with short complete sentences, then join them in a brief summary

1. during what period ha the use  of electrical energy enourmosly increased ?
2. what does this increase  prove ?
3. what has the large-scale application  of electrical energy required ?
4. what type of research has alwuys been given special attention ?
5. what considerations have  led to the  selection of appropriate materials ?
6.what was done in order to improve  properties suitable  for specific purposes ?
7. did the research on known materials answer satisfactorily the requirements of the modern electrical industry ?
8. how are materials classified ?
9. the five main groups taken into account for general purposes

WORD STUDY AND PATTERNS

EITHER , WETHER , BOTH

either is used in order to emphasize an alternatives  while both will espress the combination of two thngs (nouns verbs etc.) compare the two sentences :

I hoper he can speak either French or German (I hope he speaks al least one of these languages)
either Language will do I speak both
I speak both French and German

the possibility of an alternative con also expressed emphatically by whether  which is used  when there is a strong possibility that the action or condition espressed by the verb that follo ws may no come true or may have different  result
Most time it can be replaced by if

I don't know                                                          it will work satisfactorily (or not)
you must ask                                 whether           they are ready to accept a long delivery period
it is necessary to determine                if                the voltage  applied is correct
it remains to be seen                                             the fault is caused by manipulation or defective insaulation

whether amy also refer to two  or more possibilities  which will not change what is stated  in the main  calusa
It cannot be replaced by if in this case

whether due high cost or poor efficiency this produco did not sell seccessfully on foreign markets
prices  of raw materials will increase seadily whwthwe we like it or not