New Electr-on New Electr-on Raffaella beolé • Margherita Robba ESP new series English for Specific Purposes English for Electronics, Electrotechnology, Automation and ICT
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New Electr-onNew Electr-on
Raffaella beolé • Margherita RobbaESPnew series
English for Specific Purposes
New
Electr-on
EDIS
CO
COD. 1873
€ 22,50ISbN 978-88-441-1873-0
Book + CD
Questo volume, sprovvisto di talloncino afronte, � da considerarsi copia di SAGGIO-CAMPIONE GRATUITO , fuori commercio(vendita e altri atti di disposizione vietati:art. 17, L. 633/1941). Esente da I.V.A.(D.P.R. n. 633/1972, art. 2).
New Electr-on consists of a:
– Student’s book
– Teacher’s Guide with teaching notes, transcripts and
answer key
– Audio CD
New Electr-on is designed for:
– students who have already taken a basic English
course
– anyone who works in the field of Electronics,
Electrotechnics, Automation and ICT
The ESP series has been planned to:
– improve reading comprehension skills by using
authentic technical material together with vocabulary
and language activities
– develop writing skills
– encourage students to speak freely in English
– improve listening comprehension
Other titles are:
• Agriculture
• A Matter of Life
• Chemistry
• Landscapes
• Mechways
NLINE RESOURCES • Teacher’s Guide • Transcripts • Further Activities
• I-Tech
• Advertising and Promotion
• The World of Fashion
• Deep into Society
New Electr-onESPESP
new series
English for Specific Purposes
English for Electronics, Electrotechnology,
Automation and ICT
Raffaella Beolé • Margherita Robba
New Electr-onEnglish for:
• Electronics, Electrotechnology and Automation• Information and Communication Technology
New Electr-onRealizzazione editoriale:– Progetto e consulenza: Raffaele Polichetti– Revisione linguistica: Stefan Cooper– Progetto grafico e impaginazione: G&B - Torino– Disegni: Mauro Borgarello– Revisione testi: Paola Ghigo– Registrazione audio: Ivano Atzori
Ai sensi dell’art. 5 della Legge 169/2008, l’Editore si impegna a mantenere invariato il contenuto della presente opera per almeno un quinquennio dall’anno di pubblicazione. Eventuali aggiornamenti e/o materiali di approfondimento saranno resi disponibili on-line sul sito www.edisco.it.
L’Editore dichiara che l’opera è conforme alle Norme e Avvertenze tecniche per la compilazione dei libri di testo emanate dal Ministero dell’Istruzione, dell’Università e della Ricerca.
I processi di progettazione, produzione e commercializzazione della Casa Editrice sono effettuati secondo la norma UNI EN ISO 9001:2000 (Vision 2000).
L’Editore mette a disposizione degli studenti non vedenti, ipovedenti, disabili motori o con disturbi specifici di apprendimento i file pdf in cui sono memorizzate le pagine di questo libro. Il formato del file permette l’ingrandimento dei caratteri del testo e la lettura mediante software screen reader.
Tutti i diritti riservatiCopyright © 2012 Edisco Editrice, Torino10128 Torino – Via Pastrengo, 28Tel. 011.54.78.80 – Fax 011.51.75.396e-mail: [email protected] • sito web: www.edisco.it
I diritti di elaborazione in qualsiasi forma o opera, di memorizzazione anche digitale su supporti di qualsiasi tipo (inclusi magnetici e ottici), di riproduzione e di adattamento totale o parziale con qualsiasi mezzo (compresi i microfilm e le copie fotostatiche), i diritti di noleggio, di prestito e di traduzione sono riservati per tutti i paesi. L’acquisto della presente copia dell’opera non implica il trasferimento dei suddetti diritti né li esaurisce.
Le fotocopie per uso personale (cioè privato e individuale) possono essere effettuate, nei limiti del 15% di ciascun volume, dietro pagamento alla S.I.A.E. del compenso previsto dall’art. 68, commi 4 e 5, della legge 22 aprile 1941 n. 633. Tali fotocopie possono essere effettuate negli esercizi commerciali convenzionati S.I.A.E. o con altre modalità indicate da S.I.A.E.
L’Editore è a disposizione degli aventi diritto con i quali non gli è stato possibile comunicare, nonché per eventuali involontarie omissioni e inesattezze nella citazione delle fonti dei brani, illustrazioni e fotografie riprodotti nel presente volume.
Stampato per conto della Casa editrice pressoGEDA, Nichelino (To), Italia
Printed in Italy
Ristampe
5 4 3 2 1 0 2018 2017 2016 2015 2014 2013
Presentazione
L’argomentoNew Electr-on è rivolto agli studenti dei corsi di studio a indirizzo:
• Elettronica ed Elettrotecnica (indirizzo C3) e le sue aree opzionali di approfondimento, Elettronica, Elettrotecnica ed Automazione;
• Informatica e Telecomunicazioni (indirizzo C4) e le sue omonime aree opzionali di approfondimento.
I contenuti sono stati ordinati secondo criteri di graduale complessità concettuale e linguistica e vengono esplorati utilizzando le quattro abilità in modo omogeneo ed integrato. Gli argomenti scelti riflettono le aree di studio in L1. I brani, tutti autentici, offrono un assortimento di stili, registri e livelli di difficoltà e sono tratti da fonti diverse: giornali e riviste specializzate, testi scolastici inglesi e americani, materiale promozionale, manuali tecnici e siti internet.
La strutturaNew Electr-on è diviso in sei Moduli, ognuno dei quali è ripartito in due sezioni:
1 Technical Section – Divisa in Unità, contiene testi e attività che riguardano i contenuti specifici della specializzazione già affrontati in L1. Ogni Unità è suddivisa in Capitoli per favorire non solo uno studio più parcellizzato, ma anche la scelta antologica da parte dell’insegnante. I testi vengono affrontati in modo graduale, attraverso esercizi di Before Reading, While Reading, esplorazione del lessico tecnico, comprensione scritta e/o orale, globale e specifica. Brevi ‘box’ di approfondimento, denominati Moving Deeper, permettono di ampliare le conoscenze sull’argomento. Un ricco apparato iconografico (con funzioni esplicative non solo esornative) correda i testi, per ognuno dei quali è previsto un esauriente glossario.
2 Language Section – Si occupa di contenuti inerenti alla disciplina ponendo particolare attenzione all’arricchimento lessicale e strutturale, allo sviluppo delle quattro abilità linguistiche e al potenziamento della lingua tramite materie in inglese e certificazioni linguistiche. Presenta le seguenti ripartizioni:
A. REVISING & EXPLOITING • Vocabulary. Comprende specifiche attività per il consolidamento del lessico
tecnico più importante del Modulo.• Assignment. Presenta compiti che gli studenti possono svolgere a casa come
rinforzo e ripasso degli argomenti del Modulo.• Research Projects. Suggerisce spunti per ricerche in rete.• Grammar. Propone il rinforzo delle strutture morfo-sintattiche più ricorrenti nel
linguaggio tecnico.
B. SKILLS• Offre testi ed attività di consolidamento dei contenuti appresi per sviluppare le
quattro abilità linguistiche: Reading, Listening, Speaking, Writing.
C. LANGUAGE IMMERSION• CLIL (Content and Language Integrated Learning). Alla fine di ogni Modulo
è presente un CLIL CORNER che si collega alle tematiche presentate in alcune delle discipline curriculari – Fisica, Tecnologia, Matematica, Diritto ed Economia, Storia, Letteratura. Questo perché gli argomenti proposti possono favorire una didattica cross-curricolare, coinvolgendo docenti delle materie citate per eventuali approfondimenti e/o progetti che permettono concretamente di studiare il medesimo contenuto da diverse prospettive.
• IELTS (International English Language Testing System). Viene offerta la possibilità di prendere dimestichezza con il più popolare test al mondo per la certificazione del livello di conoscenza della lingua inglese. Il test valuta in modo accurato la capacità di comunicare in inglese considerando situazioni che si verificano nella vita reale e professionale. IELTS incrementa le opportunità di studio e lavoro in Italia e all’estero.
materiaLi aCCessori• Teacher’s Guide – Con le chiavi di soluzione degli esercizi, i transcripts delle attività di
ascolto, note didattiche, prove di verifica collegate ai singoli Moduli e simulazioni della terza prova dell’Esame di Stato.
• CD audio di 74' – Registrato con l’impiego di speakers madre-lingua, rende più facile la pronuncia e l’apprendimento della terminologia tecnica, oltre ad essere lo strumento per svolgere le attività di ascolto.
Contents
UNIT 1 What is electricity?A. Some history ................................................ 10B. Atoms, the building blocks ........................... 16C. What is static electricity? .............................. 18
UNIT 2 Moving charges and electric currentA. Electricity and current flow ........................... 20B. Moving electrons ......................................... 21C. Types of current ........................................... 23D. Measuring electric current ............................ 25E. Resistance .................................................... 27F. Inductance ................................................... 28G. Battery basics ............................................... 28
UNIT 3 Electric circuitsA. What is an electric circuit? ............................ 30B. Closed, open and short circuits ..................... 32C. Series and parallel circuits ............................. 34D. Electric shock ................................................ 37
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UNIT 4 Energy sourcesA. Hydroelectric power plants ........................... 40B. Thermoelectric plants ................................... 42C. Nuclear power plants ................................... 43D. Solar energy ................................................. 46E. Wind energy ................................................ 48F. Tidal energy ................................................. 49G. Geothermal and biomass energy .................. 50
UNIT 5 Generating electricityA. AC/DC electricity and generators ................. 52B. The electric motor ........................................ 55C. Transformers ................................................ 56D. Rectifiers and diodes .................................... 57E. The grid ....................................................... 59
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects• Grammar (Prepositions, The Article) ....................60
skiLLs Listening (Edison’s life) .........................................64 Speaking (Ten energy-saving tips) ........................65 Reading (The hybrid car) ......................................66 Writing (How to write an application letter) ........67
Language immersionCLiL: Physics(Nuclear Fission) ...............................68ieLts: Academic Writing 1 .....................................70
UNIT 1 First stepsA. Milestones in electronics ............................... 74B. What is electronics? ..................................... 77C. Electronic functions ...................................... 79D. Electronic passive components ..................... 80E. Electronic active components ....................... 85
UNIT 2 Electronic circuitsA. Breadboards ................................................. 88B. Printedcircuitsboards .................................. 90C. Doping semiconductors ................................ 91D. The invention of the integrated circuit .......... 92E. What is an integrated circuit? ....................... 93
eLeCtroniCs2 F. New scale of integration: WSI, SOC and 3D-IC ................................... 95G. Timer circuits and counters ........................... 97
UNIT 3 AmplificationA. What is an amplifier? ................................... 98B. Operational amplifiers ................................ 101
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects•Grammar (Relative Pronouns, Costruzione a sinistra) ............. 104
skiLLs Listening (Chip production today) ......................108 Speaking (The resistor colour code) ....................109 Reading (Electronics in Medicine) ......................110 Writing (How to write a C.V.) ............................111
Language immersionCLiL: Technology (Properties of materials) ...........112ieLts: Academic Reading 1 ..................................114
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UNIT 1 Digital electronics
A. Analogue and digital circuits ....................... 118B. The binary system ...................................... 121C. Logic gates and the truth table ................... 123D. ElectroniclogicandPICs ............................. 125E. The microprocessor .................................... 126
UNIT 2 Computers outside
A. A short history ............................................ 128B. What is a computer? .................................. 132C. Computer types and sizes ........................... 133D. Personalcomputertypes ............................ 135E. Computer components ............................... 137F. Hardware: input devices ............................. 138G. Hardware: output devices .......................... 141H. Software .................................................... 143I. Operating systems ..................................... 144J. Levels of programming languages .............. 145
UNIT 3 Computers inside
A. TheCPU .................................................... 146B. HowdoestheCPUwork? .......................... 148C. The information processing cycle ................ 150D. Main data storage ...................................... 153E. Backing storage .......................................... 154F. ThePCmodesofoperation ........................ 157G. Database .................................................... 159H. Data security .............................................. 160
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects• Grammar (Modal Verbs, The Passive Voice) .......162
skiLLs Listening (Mission Impossible) ...........................166 Speaking (In a computer shop) ...........................167 Reading (System analysis) ..................................168 Writing (Using computers in schools) .................169
Language immersionCLiL: Mathematics (Boolean Algebra) ..................170ieLts: SpeakingSection(Part1) ...........................172
UNIT 1 Communications and telecommunications
A. From simple wires to huge networks .......... 176B. Telecommunications ................................... 181C. What is information? .................................. 182D. Transmission media: wires and cables ......... 183E. Optical fibres .............................................. 185F. Air transmission: antennas .......................... 188G. Satellites ..................................................... 189
UNIT 2 Communication icons
A. The radio .................................................... 192B. The television ............................................. 195C. Cathode ray tube and plasma display ......... 197D. Fixed telephone .......................................... 200E. Cellular phones .......................................... 202F. What is a smartphone? .............................. 205
UNIT 3 Networks
A. LANs and WANs ........................................ 206B. Network topologies .................................... 210C. Wireless communication ............................. 215D. Why Wi-Fi? ................................................ 216E. Network software and protocols ................ 217F. Cloud computing ....................................... 218
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects•Grammar (Comparatives and Superlatives, Linkers [1]) .........220
skiLLs Listening (How popular are mobile phones?) ....224 Speaking (Buying a new TV) ..............................225 Reading (What is the Global Positioning System?) 226 Writing (Writing in English) ................................227
Language immersionCLiL: Law & Economics (Citizenship: information privacy laws) ...........................228ieLts: Listening Section ........................................230
UNIT 1 The Internet basics
A. What is the Internet? ................................. 234B. The Internet: some historical facts .............. 236C. Internet access ........................................... 237D. The Web .................................................... 240E. How to get started ..................................... 242F. Surfing the Net ........................................... 244G. The flow of information ............................. 245
UNIT 2 Exploiting the Net
A. How to search ............................................ 246B. Electronic mail (email) ................................ 248
C. Social network websites ............................. 251D. File sharing and downloading ..................... 254E. On-line shopping ...................................... 255
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects• Grammar (Linkers [2], Prefissi e suffissi) .............256
skiLLs Listening (An interview with Mr. X)....................260 Speaking (Finding a place to meet) ....................261 Reading (Safety on the Net) ...............................262 Writing (How to write a complaint letter) ..........263
Language immersionCLiL: History (The Cold War) ...............................264ieLts: SpeakingSection(Part2) ...........................266
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UNIT 1 AutomationA. What is automation? .................................. 270B. Handling the automation process ............... 272C. ProgrammedcommandsinCNCsystems ... 275D. Computer-assisted technologies ................. 277E. Automation and society ............................. 279
UNIT 2 RoboticsA. What is a robot? ........................................ 280B. What a robot looks like .............................. 282
C. Why a robot? ............................................. 285D. Mobile robots ............................................. 286E. Artificial intelligence ................................... 288
Language seCtionrevising and exPLoiting Vocabulary•AssignmentResearchProjects• Grammar (Phrasal verbs) ....................................290
skiLLs Listening (An interview with CYB026M) ............294 Speaking (How to describe a photo)...................295 Reading (An advertising brochure) .....................296 Writing (I, Robot) ...............................................297
Language immersionCLiL: Literature (Isaac Asimov) ............................298ieLts: Academic Writing 2 ...................................300
Unit 1 What is electricity?A. Some historyB. Atoms, the building blocksC. What is static electricity?
Unit 2 Moving charges and electric currentA. Electricity and current flowB. Moving electronsC. Types of currentD. Measuring electric currentE. ResistanceF. InductanceG. Battery basics
Unit 3 Electric circuitsA. What is an electric circuit?B. Closed, open and short circuitsC. Series and parallel circuitsD. Electric shock
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Unit 4 Energy sourcesA. Hydroelectric power plantsB. Thermoelectric plantsC. Nuclear power plantsD. Solar energyE. Wind energyF. Tidal energyG. Geothermal and biomass energy
Unit 5 Generating electricityA. AC/DC electricity and generatorsB. The electric motorC. TransformersD. Rectifiers and diodesE. The grid
Language skills Operational aims
◆ to understand what electricity is and how it is measured◆ to learn about different kinds of
electric circuits◆ to get information about energy
production and transmission
Reading:
◆ understanding the main topic(s) of a text◆ looking for specific information◆ selecting true/false statements◆ labelling pictures◆ answering questions◆ matching words and definitions ◆ translating into your language◆ filling in charts
Listening:
◆ getting the general gist of a text◆ getting specific information
Speaking:
◆ exchanging information◆ reporting to the class/teacher◆ correcting false statements
Writing:
◆ filling in charts◆ completing sentences◆ summarising◆ sending an application letter
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1 What is electricity?
600 BC: Static electricityThales, a Greek, found that when amber (fossilized ..........................) was rubbed with silk it attracted feathers and other light .......................... . He had discovered static electricity. The Greek word for amber is elektra, from which we get the words electricity and .......................... .
1600: William Gilbert invented the term electricityGilbert, scientist and physician to Queen Elizabeth I,
invented the term electricity. He was the first person to describe the earth’s magnetic .......................... and to realise that there is a relationship between
.......................... and electricity.
1663: Otto von Guericke invented the first electric generatorVon Guericke invented a generator that produced electricity by applying friction using a pad onto a rotating glass globe, but he did not recognize the .......................... generated as static electricity.
1705: Francis Hauksbee invented neon lightHauksbee created electrical effects by putting mercury into a glass globe, pumping out the air and then spinning the globe. When he did this in
1 Listen to the recording and fill in the blanks with the words given below.
effect – electronics – field – magnetism – metalobjects – politician – resin – silver
This Unit deals with how electricity was discovered and how scientists worked
to show its existence and establish laws and principles related to it.
It also revises the structure of the atom and its components.
a. some history
A spider in amber
the dark, and then rubbed the globe with his bare hand, it glowed. He did not realise it, but he had invented the neon light!
1752: Benjamin Franklin proved that lightning is a form of electricityFranklin, a famous U.S. .........................., flew a kite with a metal tip in a thunderstorm to prove that lightning is a form of electricity.
1780: Luigi Galvani’s dead frog’s legsGalvani discovered that when he touched a dead frog’s leg with a knife, the leg twitched violently. Alessandro Volta later showed that this was because electricity is created when moisture (from the frog) comes between two different types of .......................... (the steel knife and a tin plate).
1800: Alessandro Volta’s PileVolta created the first simple battery. He used pure .......................... and zinc discs, sandwiched between muslin damped in a salt solution, developed from Galvani’s earlier experiments with a frog’s leg.
1800: Sir Humphry Davy discovered electrolysisDavy discovered that when he passed an electric current through some substances
Choose the correct alternative.
a. The word electricity comes from 1. Latin. 2. Greek. 3. English.
b. … are the most basic material in universe 1. Atoms 2. Elements 3. Electrons
c. An electron is the smallest part of 1. an atom.
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2. an element. 3. a nucleus.
d. All atoms 1. are alike. 2. belonging to the same elements are alike. 3. are different.
e. Electrons 1. orbit the protons. 2. orbit the neutrons. 3. orbit the nucleus.
Volta’s piles
to glow: illuminarsi
moisture: umidità
muslin: mussola
pad: tavoletta
spin: ruotare
to twitch: contrarsi
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they decomposed. This process later became known as electrolysis.
1820: Hans Christian Oersted discovered magnetic fields caused by electricityOersted, a Dane, found that when electricity flows through a wire, it produces a magnetic field that affects the needle of a nearby compass.
1821: Michael Faraday’s discovery that led to the invention of electric motorsFaraday discovered that when a magnet is moved inside a coil of copper wire, a tiny electric current flows through the wire. This discovery later led to the invention of electric motors.
1821: thomas Johann Seebeck discovered thermo-electricitySeebeck found that when the junction of certain metals is heated, electricity flows as thermo-electricity.
1826: André Ampère explained the electro-dynamic theoryAmpère published his theories about electricity and magnetism. He was the first to explain the electro-dynamic theory. The unit of electric current was named after him.
1827: Georg Ohm published his complete mathematical theory of electricityGerman college teacher Ohm published his
m o d u l e 1
An old telegraph
complete mathematical theory of electricity. The unit of electrical resistance was later named after him.
1829: Joseph Henry’s discovery in electromagnetismHenry showed that a wire wrapped in coils produces greater electromagnetism than a straight one. A year later, he discovered the principles of the dynamo.
1831: Michael Faraday demonstrated electromagnetic inductionFaraday demonstrated electromagnetic induction by passing a magnet through a coil of wire.
1831: the first telegraph machineCharles Wheatstone and William Fothergill Cooke created the first telegraph machine.
1834: Charles Wheatstone measured the velocity of electricityWheatstone used a revolving mirror and four miles of wire to measure the velocity of electricity.
1838: Samuel Morse invented Morse codeAt an exhibition in New York, Samuel Morse demonstrated his new telegraph machine sending 10 words a minute. He used a system of dots and dashes, which later became standard throughout the world, known as Morse code.
1870s: thomas Edison built a DC electric generatorEdison built a DC (direct current) electric generator in America. He later provided all of New York’s electricity.
1878: Joseph Swan demonstrated the first electric lightSwan, a British scientist, demonstrated the first electric light with a carbon filament lamp. A few months later, Edison made the same discovery in America.
1880s: the Wimshurst machine was inventedThis is used to produce static electricity easily and reliably. Two parallel plates are rotated in opposite directions, producing a charge around the edges of the plates. The charge is collected by a system of combs.
1880s: nikola tesla developed an AC motorTesla developed an AC (alternating current) motor and a system of AC power generation. Edison saw Tesla’s system as a threat to his DC supply and spread stories that it was not safe. But after Tesla’s system was used to power 100,000 electric lights at Chicago’s World Fair in 1893, AC became the established power supply in the USA.
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WHAT Is ElECTrICITy? u n i t 1
Try to remember what you have read in the previous text and fill in the blanks with the names of the inventors/scientists.
a. The unit of electric current was named after him. ....................................................................................
b. He demonstrated electromagnetic induction. .............................................................................................
c. He discovered that electricity can create magnetic fields. ......................................................................
d. Showing that a wire in coils produces a greater electromagnetism than a straight one,
he discovered the dynamo. ..............................................................................................................................
e. He was able to measure the velocity of electricity. ...................................................................................
f. He transmitted messages using a system of dots and dashes. ..............................................................
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1880s: nikola tesla invented the tesla coilTesla used the Tesla coil to step up ordinary household current to produce extremely high frequency current. Tesla used this high frequency current to develop some of the first neon and fluorescent lights.
1881: the first public electricity supplyThe first public electricity supply was generated in Godalming, Surrey, England, using a waterwheel at a nearby mill.
1883: Magnus Volks built the first electric railwayThe first electric railway, built by electrical engineer Magnus Volks, opened on the seafront in Brighton, England. The Volks Railway, built just for pleasure rides, is one mile long and still runs during the summer season.
1884: Charles Parsons built his first turbineParsons built his first turbine: a type of engine operated by jets of high pressure gases. This type of engine was later developed to drive the propellers of ships, including the Titanic.
affect: influenzare
coil: bobina
comb: pettine
household: domestica
mill: mulino
to spread (spread-spread-spread): diffondere
threat: minaccia
tiny: minuscolo
wrapped: arrotolatoglos
sary
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m o d u l e 11886: Heinrich Hertz produced and detected electric waves in the atmosphere
1890: turbine driven generatorsTurbine driven generators were introduced to produce electricity.
1892: Hendrik Lorentz published his electron theory
1895: Discovery of X-raysThe German physicist Wilhelm Roentgen discovered invisible rays that made a distant screen glow and passed through objects. These were X-rays.
1896: nikola tesla’s hydroelectric power generatorsTesla’s hydroelectric power generators at Niagara Falls came into operation. Within a few years, these generators were supplying electricity to New York City for the elevated railways, the subways and even the lights on Broadway.
1897: Guglielmo Marconi’s radio messageMarconi sent a radio message from the Isle of Wight to Poole (20 miles away). Later he sent a message across the Atlantic.
1905: Albert Einstein and photovoltaic cellsEinstein demonstrated that light energy could be used to produce electricity and the idea behind photovoltaic cells was born.
1918-19: Washing machines and refrigeratorsElectric washing machines and refrigerators first became available.
1926: First national Grid was introduced
1930-40s: Hydro-electric power stationsHydro-electric power stations were built in Scotland and Wales, but most electricity was generated by burning coal.
1930-40s: Electrical household appliances introducedRadios, vacuum cleaners, irons and fridges were becoming part of every household.
1936: John Logie Baird pioneered the television
1956: First large-scale nuclear power stationThe world’s first large-scale nuclear power station opened at Calder Hall in Cumbria, England.
1960s: the UK decided to develop advanced gas cooled reactors Around the same time, France and the USA decided to adopt water cooled reactor technology.
1994: the UK’s first pressurised water reactorThe UK’s first pressurised water reactor (PWR) was opened at Sizewell B in Suffolk, England.
2000: the world’s first commercial wave power stationThe world’s first commercial wave power station, on the Scottish island of Islay, began to generate electricity. Devices placed on the shoreline or out at sea use wave motion to compress air to drive a turbine or hydraulic pumps.
Nikola Tesla
National Grid: rete elettrica nazionale
shore line: costiera vacuum cleaner: aspirapolvere
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WHAT Is ElECTrICITy? u n i t 1In turns, ask and answer the following questions.
a. Who first demonstrated how to create light with a carbon filament?
b. How was the first public electricity supply generated?
c. When and where was the first electric railway built?
d. Who detected electric waves?
e. What is Wilhelm Roentgen famous for?
f. When was the idea behind photovoltaic cells born?
g. During which decades were many household appliances introduced?
h. Who was the man who first devised the television?
i. Where was the world’s first large-scale nuclear power station opened?
j. How did the world’s first commercial wave power station work?
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Tesla and Marconi: who is the father of wireless transmission?
In 1894, Tesla demonstrated his wireless communication device, (radio). His Tesla coils, he claimed, would allow him to both receive and transmit radio signals that were tuned to resonate at the same frequency. This frequency being the same, the signals would magnify incoming electrical energy via resonant action. By 1895, he had planned to transmit a signal at least 50 miles, but both his work and the lab were destroyed in a fire.At the same time, in England, Guglielmo Marconi was working on a device for wireless telegraphy that he than patented in 1896. Marconi set up a demonstration a little later, using a Tesla oscillator to transmit his signals across the English Channel.
Tesla was a great inventor. Looking back at the previous texts write a short summary about his inventions (about 100 words).
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Guglielmo Marconi
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B. atoms, the BuildiNg Blocksm o d u l e 1
Match each of the following words, taken from the text below, with their synonym/definition.
a. matter 1. small part
b. tiny 2. stuff, material
c. particle 3. extremely small
d. basic 4. main, fundamental
5
Atoms are the basis for everything in the universe. Matter is composed of atoms. Atoms are composed of pieces of matter like neutrons, electrons, and protons. There are even smaller particles moving around in atoms, inside the protons and neutrons. Scientists have many names for those pieces, but you may have heard of nucleons and quarks. Nuclear chemists and physicists work with particle accelerators to discover the presence of these pieces of matter. As you know, there are over 100 elements in the periodic table. What makes each of those elements different is the number of electrons, protons, and neutrons. The protons and neutrons are always in the center of the atom. Scientists call the center of the atom the nucleus. The electrons move around the center in areas called orbitals. You can also see that each piece has either a “+”, “–”, or a “0” symbol, which refers to the charge of the particle. Shocks from a socket, static electricity or lightning are all different types of electric charge. There are even charges in tiny particles of matter like atoms: the electron always has a “–” or negative charge; the proton always has a “+” or positive charge. If the charge of an entire atom is “0”, it means there are equal numbers of positive and negative pieces, equal numbers of electrons and protons. The third particle is the neutron. This has a neutral charge (a charge of zero). When electrons leave their orbit, they move from atom to atom at random, drifting in no particular direction. Electrons that move in such a way are referred to as free electrons.However, a force can be used to cause them to move in a given direction. That is how electricity is generated.
It’s like this…
electron (–)
proton (+)
neutron (0)
neutron:large with no charge
proton:large with
positive charge
0
+
electron:small with
negative charge–
17
WHAT Is ElECTrICITy? u n i t 1Test your knowledge about atoms by doing this quiz. Tick the right answers.6
a. Which of these is NOT one of the basic pieces of an atom? Electron Quantron Proton Neutron
b. Which atomic particles will you find inside of the nucleus of an atom? Electron and proton Proton and neutron Neutron and electron
c. Which atomic particle has a negative charge? Electron Proton Neutron None of the above
d. An electron has a mass that is much less than a proton’s. True False
e. Electrons can be found in the nucleus. True False
f. An atom with a neutral charge has the same number of protons and neutrons. neutrons and electrons. protons and electrons.
g. There is no particle of matter smaller than an atom. True False
h. Atoms of an element may have more or less neutrons or electrons than other atoms of the same element. True False
Ask and answer the following questions in turns.
7
a. What is an atom?
b. Are atoms all alike?
c. What does their nucleus consist of?
d. How does an electron fit into an atom?
e. When does an atom have a charge equal to “0”?
f. What are free electrons?
Write down the answers to the questions above and, using suitable linkers, join them to write a short text.
8
An atom is .................................................................
.......................................................................................
.......................................................................................
.......................................................................................
.......................................................................................
.......................................................................................
.......................................................................................
.......................................................................................
18
c. What is static electricity?m o d u l e 1
Atoms usually have the same number of electrons and protons. In this case, the atom has no charge, it is “neutral.” But if you rub two objects together, electrons can move from one atom to another. Some atoms get extra electrons and have a negative charge; other atoms lose electrons and have a positive charge. When charges are separated like this, it is called static electricity. If two things have different charges, they attract, or pull towards each other; if they have the same charge, they repel, or push away from each other.
So why does your hair stand up when you take your hat off? When you take your hat off, it rubs against your hair. Electrons move from your hair to the hat. Now each of the hairs has the same positive charge since things with the same charge repel each other, the hairs try to move away from each other. The farthest they can go is to stand up and away from all the other hairs. If you walk across a carpet, electrons move from it to you and you have extra electrons if you now touch a door knob, the electrons move from you to the knob and you get a shock.
19
WHAT Is ElECTrICITy? u n i t 1Cover the text above and try to explain in your words what static electricity consists of. Mention the examples given.
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
....................................................................................................................................................................................
9
What is the electromagnetic spectrum?
radiation is a type of energy that moves in the form of waves or particles. This energy is emitted by one body, travels through a substance or space, reflected by some bodies, and is ultimately absorbed by another body. Different kinds of radiation differ in their wavelengths and energy. As the wavelength of radiation increases, the amount of energy decreases. The diagram shows the different types of electromagnetic radiation. This list is called the electromagnetic spectrum. The only type of radiation that people can see is visible light. Notice that visible light is made up of the colours of the rainbow (red, orange, yellow, green, blue, indigo and violet). Violet light has the shortest wavelength and the most energy. Red light has the longest wavelength and the least energy.
RADIO
MICROWAVE
INFRARED
VISIBLELIGHT UV
X-RAY
GAMMA
HIGH-ENERGY
WAVELENGHT
ENERGY
5,000,000,000
0.000000248
10,000
0.124
500
2.48
250
4.96
0,5
2480
0,0005
2,480,000
nanometers
electron volts
1 cm= 10,000,000 nanometers
20
uN
it
2 moviNg charges aNd electric curreNt
When we separate electrons and protons, the result of our work will be a charge. This will have a potential.Basically speaking, the quantity of any charge can be measured by its force to repel or attract and the potential to move another charge, either by attraction or by repulsion. There is always a difference of potential between two different
This Unit looks at how an electric current is generated, how it moves through
materials and how it can be measured.
a. electricity and curreNt floW
charges. When this difference in potential forces a third charge to move, the moving charge is an electric current. Electricity is defined as the flow of free electrons along a conductor and when this occurs, it is commonly referred to as current flow. To produce this flow, a charge must be moved by a generator placed at one end of the conductor.
In the text above, find the English equivalents of the Italian words below.
a. qualsiasi .......................................................................
b. respingere .......................................................................
c. attrarre .......................................................................
d. o... o... .......................................................................
e. costringe .......................................................................
f. flusso .......................................................................
g. si verifica .......................................................................
h. comunemente .......................................................................
i. posto (part. passato) .......................................................................
j. estremità .......................................................................
1
Conductors – A material through which electricity can pass easily is called a conductor, which offers very little resistance or opposition to the flow of electrons.To some extent, all metals are conductors of electricity, although some are much better than others because of the presence of many free electrons capable of moving away from their atoms.Conductors may be in the form of bars, tubes, or sheets. The most common conductors are wires. Wires are available in many sizes, from the thickness of a hair to that of your arm. To prevent them from touching, they are usually coated with a plastic or cloth material. This covering on the conductor is called an insulator.
insulators – An insulator is a material with very few, if any, free electrons. There are no known materials which are perfect insulators, but there are materials that are such poor conductors that they are classified as insulators. Glass, dry wood, rubber, mica, and certain plastics are insu lat ing materials.
Dry air at normal temperature and average atmospheric pressure is a very good insulator, too, since its conductivity is almost zero. Thus, there is often no need to cover a conductor with a solid insulator if there is no danger of accidental contact.
Semiconductors – So far we have looked at conductors and insulators. In between the two extremes are semiconductors. Germanium and silicon are the two most commonly known semiconductor materials and, through the introduction of small amounts of other elements (called impurities), these elements become limited conductors. They are used in the manufacture of transistors and diodes and are called semiconductors because they have conductivity halfway between that of a good conductor and a good insulator.
Superconductors – Superconductors are materials that display zero resistance under certain conditions. These conditions are called the “critical temperature” and “critical field,” denoted tc and Hc, respectively. The tc is
Define electricity in your own words, then compare your definition to the one given in the following text.
21
B. moviNg electroNs
mica: mica (minerale) rubber: gomma thickness: spessore
GlossAry
22
m o d u l e 1
the highest temperature state the material can reach and remain superconductive. The Hc is the highest magnetic field the material can be exposed to, before reverting to its normal magnetic state. There are type i and type ii superconductors. type i are composed of pure substances, usually metals, and type ii are composite compounds, usually some sort of ceramic material.
Decide if the following are true or false and correct the false ones.
T Fa. A stream of electrons moving from atom to atom inside a conductor produces an electric current. b. Electrons move easily through any material.
c. What makes a material a good conductor is the presence of free electrons.
d. There are materials which are perfect insulators.
e. Limited conductors have a very limited use in electronics.
f. Impurities are removed to improve the performances of some elements in the manufacturing of electronic components.
g. Superconductors show zero resistance in all condictions.
h. All superconductors consist of extremely pure materials.
2
RESISTANCE IN OHMS PER CUBIC CENTIMETER
0.00
0001
0.00
001
0.00
01
0.00
1
0.01
0.1
1 10 100
100
0
1000
0
100
000
100
000
0
100
000
000
1016
1018
SILVERCOPPER
ALUMINIUMIMPURE GERMANIUM
TRANSISTOR GERMANIUMTRANSISTOR SILICON
PURE GERMANIUMPURE SILICON
WOODGLASSMICA
POLYSTYRENE
conductors
semiconductors
insulators
Insulators, semiconductors, and conductors in terms of inherent resistance.
23
MovING CHArGEs AND ElECTrIC CUrrENT u n i t 2
DC/Direct Current – Direct Current is the continuous ......................... of electrons in one direction and it ......................... changes its direction as long as the power is applied or an appliance using the current is switched on. The magnitude of a direct current can change, but ......................... its direction. It can be produced by ............................., fuel cells, rectifiers and ......................... with commutators. It was supplanted by alternating current for common commercial power in the late 1880s because it was then ..........................to transform it to the high voltages needed for ...................
.............. distance transmission (direct current cannot use transformers to change voltage). Techniques developed in the 1960s overcame this .................................. and direct current is now transmitted over long..........................., though it has to be converted to ................................ current for final distribution. It has several relevant uses in .............................. motors and generators. In cars, it supplies the current needed to charge the battery to operate the ignition system, the lights, the windscreen wipers, etc.
AC/Alternating Current – Alternating current changes its direction of flow as it moves along a wire. It flows in one direction, then in the other, constantly changing. It changes magnitude and direction intermittently because of the way it is generated, in periods of time called cycles. The term frequency is used to describe how many times it changes its direction in one second. The AC we use at home changes direction 60 times per second. It has a frequency of 60 Hz (hertz). It is said to be 60-Hz AC.Alternating current can also be expressed in megahertz or MHz (one million Hz per second), or Kilohertz (one thousand Hz per second).AC has a great advantage over DC: it can be transported over long distances through small wires thanks to the higher voltages and lower currents.
c. types of curreNt
3 While reading, listen to the recording and fill in the blanks with the words given below.
distances – generators – alternating – uneconomical – never – not – electricobstacle – batteries – flow – long
max position B90°
zeroposition C
180°
position D0° or 360°
270°position D max
0A
0
DC
AC
The sine wave Comparison of AC to DC
ignition: accensione
to supplant: sostituire
windscreen wipers: tergicristalli
glos
sary
Building a stator for an electric generator
24
m o d u l e 1
Complete the following sentences referring back to the text on AC and DC.
a. A flow of electric charge which never changes ............................................................... .
b. In the late 1880s, AC replaced ...................... because ............................................................... .
c. Direct current must normally be ............................................................... before being transmitted for final distribution.
d. As it flows along a wire, ....................................................... constantly ..................................................... .
e. The term....................................................... to describe how often AC changes its direction ...........
....................................................... .
f. We name 60 Hz AC .............................................................................................................. .
g. MHz and kHz are respectively referred to ...................................................................................... .
h. Higher voltages and lower current allow ....................................................... over long distances.
4
Pair Work. Student A asks Student B about the characteristics of DC. Then student B asks student A about the characteristics of AC. Use the cues below to make up your dialogue:
• whatDC/ACare • howtheyareproduced • whatfrequencyis • advantagesanddisadvantages • uses
5
25
MovING CHArGEs AND ElECTrIC CUrrENT u n i t 2
Coulomb – The coulomb measures the quantity of electricity conveyed in one second by a current of one ampere. It is also about 6.241506 × 1018 times the charge of an electron.
Power – Power is defined as the rate at which the work is done. In metric measurement, it is expressed in terms of watts (W) for power and joules (J) for energy or work. A watt is the power that gives rise to the production of energy at the rate of one joule per second (W=J/s). A joule is the work done when the point of application of force of one Newton is displaced through a distance of one metre in the direction of the force (J=N × m).Power can be mechanical or electrical. The power rating of electric motors is calculated by taking the voltage and multiplying it by the current drawn under full load. This power is measured in watts. In other words 1 × 1 A = 1 W. Put into a formula it reads:
power = volts × amperes or P = E × i,where E = voltage, or emf, and i = current, or intensity of electron flow.
Volts – We measure the difference of potential between the two opposite ends of a conductor in terms of volts (V), named after the Italian scientist Alessandro Volta. This is actually the electric pressure exerted on electrons in a circuit, the pathway for the movement of electrons. An external force exerted on electrons to make them flow through a conductor is known as electromotive force, or emf. The terms electric pressure, potential difference and emf mean the same thing. A voltmeter is used to measure voltage.
Amperes – The ampere, or amp, is a measure of the amount of current flowing through a conductor, that is to say the number of electrons passing a given point on a conductor in one second. If it is equal to 6.25 × 1018 electrons in one second, it is said to be one ampere of current flowing. However, in electronics it is sometimes necessary to use smaller units of measurement. The milliampere, one thousandth (0.001) of an ampere, is abbreviated as mA; the microampere, one millionth (0.000001) of an ampere, is abbreviated as µA. The instrument used to measure current flow in a circuit is called ammeter. A milliammeter is used to measure smaller amounts, while the microammeter is used to measure extremely small amounts.
d. measuriNg electric curreNt
While reading the following text, if you have problems with measures, numbers or symbols, look them up in the Appendix under metric prefixes and powers of ten or the Greek alphabet used in electricity and electronics.
Read the following text, then fill in the chart below with the missing information.6
What? Measures what?
The number of electrons passing a given point on a conductor in one second.
The amount of power necessary for the production of energy at the rate of one joule per second.
Coulomb
pathway: tracciato
GlossAry
26
Milliwatt (mW)
This is a term used in electronics, when dealing with small amplifiers and other electronic devices. It means one thousandth (0.001) of a watt.
Ask and answer the following questions in turns.
a. What do volts measure?
b. How is emf defined?
c. How is the amount of current flowing measured?
d. What is one amp of current equal to?
e. What is the unit for measuring electric power?
f. How much is a kilowatt?
7
bill: (qui) bolletta
glossary
Kilowatt (kW)
This is a term commonly used to express the amount of used or available electric energy. The term kilo (k) means one thousand. A kilowatt is one thousand watts.When the term is used to describe the power dissipated or consumed by a home in a month, it is expressed in kilowatthours (kWh), that is to say, one thousand watts used for a period of an hour. Electricity bills are calculated on an hourly basis and then read in the kWh unit. The entire month’s time is equated to one hour’s time.
27
MovING CHArGEs AND ElECTrIC CUrrENT u n i t 2
Any time there is movement, there is resistance. Resistance is useful in electric and electronic circuits, making it possible to generate heat, control electron flow, and supply the correct voltage to a device.Resistance in a conductor depends on four factors: material, length, cross-sectional area, and temperature. • Material – Some materials offer more
resistance than others. It depends upon the number of free electrons present in the material.
• Length – The longer the conductor (wire), the more resistance it has. Resistance is said to vary directly with the length of the conductor.
• Cross-sectional area – Resistance varies inversely with the size of the conductor in cross-section. In other words, the larger the conductor (wire), the smaller the resistance per foot of length.
• Temperature – For most materials, the higher the temperature, the higher the resistance.
Resistance is measured by a unit called the ohm, after the German physicist Georg Ohm, and the Greek letter omega (Ω) is used as the symbol for electrical resistance.
e. resistaNce
Ohm’s lawGeorg Ohm discovered the relationship between voltage, current, and resistance in 1827. He found that in any circuit (the pathway along which electrons move) where the only opposition to the flow of electrons is resistance, there is a relationship between the values of voltage, current and resistance. The strength or intensity of the current is directly proportional to the voltage and inversely to the resistance.We can easily work with Ohm’s law when it is expressed in the formula:
This is used to find the emf (voltage) when the current and the resistance are known.To find the current when the voltage and resistance are known, we use:
To find the resistance when the voltage and current are known, we use:
E = i × R
i = E/R
R = E/i
E = emf (voltage)I = currentR = resistence
Complete the following sentences.
a. Resistance makes it possible to ................................................................................. in electric and electronic circuits.
b. The number of free electrons in a material determines .........................................................................
............................................................................................................................................................................. .
c. If conductor A is shorter than conductor B, it will have a ................................................ .
d. If conductor A has a ............................................. cross-sectional area, it will have a higher resistance per foot of length.
e. Resistance is ......................................................................... to temperature for most materials.
8
28
m o d u l e 1
Inductance is the property of a conductor (often in the shape of a coil) that is measured by the size of the electromotive force, or voltage, induced in it, compared with the rate of change of the electric current that produces the voltage. A steady current produces a stationary magnetic field; a steadily changing current, alternating current, or fluctuating direct current produces a varying magnetic field, which, in turn, induces an electromotive force in a conductor that is present in the field. The size of the induced electromotive force is proportional to the rate of change of the electric current. This proportionality factor is called the inductance and is defined as the value of the electromotive force induced in a conductor divided by the magnitude of the rate of change of the current causing the induction.
9 There are seven wrong terms in the text below. Listen to the recording while reading it and replace them with the correct ones.
If you look at any battery, you will notice that it has two terminals. One terminal is marked (+), or positive, while the other is marked (–), or negative. In an AA, C or D cell (normal flash-light batteries), the ends of the battery are the terminals. In a common car battery, there are two heavy lead posts that act as the terminals. Electrons collect on the negative terminal of the battery. If you connect a wire between the negative and positive terminals, the electrons will flow from the negative to the positive terminal as slowly as they can (and wear out the battery very quickly – this also tends to be dangerous, especially with large batteries). Normally, you connect some type of load to the battery using the wire. The load might be something like a light bulb, a motor or an electronic chip. Outside the battery itself, a mechanical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery internal resistance) controls how many electrons can flow between the terminals. Electrons flow from the battery into a wire, and can travel from the negative to the positive terminal for the chemical reaction to take place. That is why a battery can sit on a shelf for a year and still have plenty of power – unless electrons are flowing from the negative to the positive terminal, the chemical reaction does not take place. Once you connect a wire, the reaction ends.
f. iNductaNce
g. Battery Basics
lead posts: accumulatori al piombo
to sit: (qui) stare
to wear out: consumare
glos
sary
a. ........................................... instead of .......................................... .
b. ........................................... instead of .......................................... .
c. ........................................... instead of .......................................... .
d. ........................................... instead of .......................................... .
e. ........................................... instead of .......................................... .
f. ........................................... instead of .......................................... .
g. ........................................... instead of .......................................... .
29
MovING CHArGEs AND ElECTrIC CUrrENT u n i t 2Write the following words on the picture in the spaces provided.
dry-cell battery – positive electrode (cathode) – light bulb – negative electrode (anode)load – external case
10
Modern battery chemistry
Modern batteries use a variety of chemicals to power their reactions. Typical battery chemistries include:Zinc-carbon battery – Also known as a standard carbon battery, zinc-carbon chemistry is used in all inexpensive AA, C and D dry-cell batteries. The electrodes are zinc and carbon, with an acidic paste between them that serves as the electrolyte. Alkaline battery – Alkaline chemistry is used in common batteries, the electrodes are zinc and manganese-oxide, with an alkaline electrolyte. lithium-iodide battery – Lithium-iodide chemistry is used in pacemakers and hearing aids because of the long life of the batteries. lead-acid battery – Lead-acid chemistry is used in automobiles, the electrodes are made of lead
and lead-oxide with a strong acidic electrolyte (rechargeable). Nickel-cadmium battery – The electrodes are nickel-hydroxide and cadmium, with potassium-hydroxide as the electrolyte (rechargeable). Nickel-metal hydride battery – This battery is rapidly replacing nickel-cadmium (rechargeable). lithium-ion battery – With a very good power-to-weight ratio, this is often found in high-end laptop computers and cell phones (rechargeable). Zinc-air battery – This battery is lightweight and rechargeable. Zinc-mercury oxide battery – This is often used in hearing-aids. silver-zinc battery – This is used in aeronautical applications because the power-to-weight ratio is good.
Electrons (e-)
Electrons (e-)
Electrons (e-)
Electrons (e-)
1. ......................................
2. ...............................
5. ....................
3. ...............................
4. ...............................
Electrolytepaste
Separator
Carbon andmanganesedioxide mixture
30
uN
it
3 electric circuits
This Unit looks at electric circuits, how they work, their components, different
types of circuits and their uses. It also deals with electric shock and the
precautions to take in order to avoid it.
a. What is aN electric circuit?An electric circuit is an unbroken path along which electric current can flow. In a circuit, the electrons flow through nodes (junction points), along branches (portions of a network consisting of one or more two-terminal elements in series) and meshes or loops (branches forming a closed path in a circuit).A simple circuit might consist of an electric cell (the power source), two conducting wires (one end of each attached to each terminal of the cell), and a small lamp (the load) to which the free ends of the wires leading from the cell are attached. A load is the device through which the electrical current flows and which changes this electrical energy into a more useful form: a light bulb changes electrical energy into light energy, an electric motor changes electrical energy into mechanical energy, a speaker in a radio changes electrical energy into sound. The source is the device which furnishes the electrical energy (the electromotive force) used by the load. It may consist of a simple dry cell (as in a torch), a storage battery (as in an automobile), or a power supply (such as a battery charger or a generator). The switch, which permits control of the electrical device, interrupts the current delivered to the load.
A circuit with nodes, branches and meshes
branch load
wire
powersource
(battery)+_
mesh
node
resistors
A simple circuit
Answer the following questions.
a. Do you know what an electric circuit is?
b. When does current flow along a circuit?
When it is open. When it is closed.
c. What happens if a short circuit occurs?
Check your answer after reading the text.
31
branch: ramo
dry cell: pila a secco
mesh: maglia
path: percorso
storage battery: batteria di accumulatori
torch: torcia elettricaglos
sary
Name the different parts of the circuit using the words below.
load device (lamp) – protection device (fuse) – control device (switch) –power source (battery) – conductor (wire)
1
.............................................
.............................................
.............................................
.............................................
.............................................
32
B. closed, opeN and short circuitsm o d u l e 1
The circuit is “closed” when the connections are made properly and current flows, so that the lamp will light. The current flows from the cell along one wire to the lamp, through the lamp, and along the other wire back to the cell. When the wires are disconnected, the circuit is said to be “open” or “broken”. In practice, circuits are opened by such devices as switches, fuses, and circuit breakers.A short circuit is an abnormal low-resistance connection between two points of different potential which causes an excessive current flow through the connection and, potentially, damage to the circuit, overheating, fire or explosion. A short circuit exists whenever the resistance of a circuit or the resistance of a part of it drops in value to almost zero ohms. A “short” often occurs as a result of improper wiring or broken insulation. To protect against short circuits, devices such as fuses or circuit breakers are used: they sense the excess current and break the circuit so that no current flows.
Fuses and circuit breakers
A fuse is a safety device used to protect an electrical circuit from the effect of excessive current. A fuse consists of a strip of a low-melting alloy enclosed in a suitable housing. It is connected in series with the circuit it has to protect. Because of its electrical resistance, the alloy strip is heated by the electric current; if the current exceeds the safe value for which the fuse was designed, the strip melts, opening the circuit and stopping the current flow.A circuit can also be protected by a circuit breaker. The most familiar household circuit breakers protect circuits against overloading or overheating, short circuits to prevent fire and electrical shock. The advantage of a circuit breaker is that it can be reset after it has been tripped, while a fuse must be replaced after it has been used once.
alloy: lega
circuit breaker: interruttore automatico
to drop: diminuire
household: domestico
housing: custodia
to melt: fondere
to sense: rilevare
strip: striscia
to trip: far scattare
glos
sary
Match the beginning of each sentence with the correct ending.
a. When a voltage source is connected to a circuit, the voltage ..........
b. If a circuit containing a voltage source is broken, ..........
c. A circuit is an unbroken loop of conductive material that ..........
d. If a circuit is “broken”, its conductive elements no longer form a complete path, ..........
e. A short circuit is an electric circuit ..........
f. An open circuit is one where the continuity ..........
g. A closed circuit is one that is ..........
h. A device designed to open or close a circuit ..........
1. .......... continuous electron flow cannot occur in it.
2. .......... the full voltage of that source will appear across the points of the break.
2
33
ElECTrIC CIrCUITs u n i t 33. .......... complete, with good continuity throughout.
4. .......... will cause a uniform flow of electrons through that circuit called a current.
5. .......... offering little or no resistance to the flow of electrons.
6. .......... allows electrons to flow through continuously without beginning or end.
7. .......... has been broken by an interruption in the path for electrons to flow.
8. .......... under controlled conditions is called a switch.
Answer the following questions.
a. What is an open circuit?
b. What is a closed circuit?
c. When does a short circuit occur?
d. What is the load in a circuit?
e. What is the source?
f. What is the function of a switch?
3
34
m o d u l e 1
In electrical circuits, series and parallel are the two basic ways of wiring components. A series circuit is the simplest circuit. The conductors, control and protection devices, loads, and power source are connected one after the other along the conducting path. The resistance of each device can be different and the total resistance is equal to the sum of the individual resistances. The same amount of current will flow through each device while the voltage will be different. Series circuits are used when small amounts of power are required, since each added resistor will cause the current in the circuit to drop. If the path is broken, no current flows and no part of the circuit works. Christmas tree lights are a good example: when one light goes out, the entire string stops working.A parallel circuit has more than one path for current flow. Each separate path is called a branch of the circuit.
Current from the source splits up and enters the various branches. When two or more components are connected in parallel the voltage is the same across all the components, the total current flowing in the circuit is shared between the components and equal to the sum of the currents in the individual branches. The total resistance is less than that of the element having the least resistance. If one branch is broken, current will
continue flowing to the other branches. Parallel circuits are found in most household electrical wiring. This is done so that lights don’t stop working just because you turned your TV off.
Many circuits combine series and parallel arrangements. One branch of a parallel circuit, for example, may have within it several objects in a series. The power source and control or protection devices are usually in series; the loads are usually in parallel. The same current flows in the series portion, different currents in the parallel portion. The same voltage is applied to parallel devices, different voltages to series devices. If the series portion is broken, current stops flowing in the entire circuit. If a parallel branch is broken, current continues flowing in the series portion and the remaining branches.
c. series and parallel circuits
Lamps
A series circuit
R1
R2
A parallel circuit
R1 R2
amount: quantità to split up: dividersi
GlossAry
35
ElECTrIC CIrCUITs u n i t 3Tick if these sentences refer to series or parallel circuits.
s P
a. The voltage divides between the loads.
b. A break in the circuit will disable the entire circuit.
c. The current flow is the same throughout the circuit.
d. The resistance of each load can be different.
e. Each branch receives source voltage.
f. Current flow through each branch can be different.
g. In the event of an opening in the circuit in one of the branches, current will continue to flow through the remaining ones.
h. The resistance of each branch can be different.
4
Answer the following questions.
a. What’s the difference between a series and a parallel circuit?
b. How is current in a series circuit?
c. How is the total resistance in a series circuit calculated?
d. When is the use of a series circuit suggested?
e. What is the main disadvantage of a series circuit?
f. How can the total current be determined?
g. What is the advantage of a parallel circuit?
h. How are devices connected in a series and a parallel circuit?
5
Circuit symbols
Open Switch Closed Switch Lamp
Cell Battery Voltmeter
Fuse Ammeter
Variable resistor Thermistor Light dependent resistor (LDR)
Resistor
Parallel and series circuits
36
m o d u l e 1Match the following words with the corresponding synonyms or definitions.
a. unbrokenb. pathc. loadd. branche. split upf. shareg. striph. alloyi. meltj. overloading
6 11. Mixture of two or more metals.12. Excessive electric charge in a circuit.13. Way.14. Uninterrupted.15. Have something in common.16. Become liquid.17. Amount of electrical power.18. Part or passage.19. Divide.10. A device that consumes electric power.
Match the beginning of each sentence with the correct ending.
a. Series and parallel 11. which passes through all the components is the same.
b. Resistance 12. the entire circuit does not work.
c. A series circuit is a circuit in which 13. the voltage is the same across all the components.
d. In a series circuit, the current 14. is equal to the sum of the individual resistances.
e. The total resistance in a series circuit 15. is equal to the sum of the currents in the individual branches.
f. If one element in series burns out, 16. series and parallel arrangements.
g. A parallel circuit is a circuit where 17. is measured in ohms.
h. In a parallel circuit, 18. are two ways of wiring components in a circuit.
i. The total current in a parallel circuit 19. the various components are connected to form separate paths.
j. Many household circuits combine 10. the components are arranged one after the other.
7
Complete the chart with the missing information.
Arrangement Current voltage Total resistance Use Advantage Disadvantage
series circuits
One component after the other
Sum of voltages in each component
Easy control of current
Parallel circuits
Inferior to the resistance of the component with the least resistance
If a branch “shorts”, items in that branch don’t work
8
d. electric shock
37
ElECTrIC CIrCUITs u n i t 3
An electric shock occurs when a person comes into contact with an electrical energy source. It is usually caused by contact with
poorly insulated wires or ungrounded electrical equipment, by using electrical equipment while in contact with water, or by
being struck by lightning. Electrical energy flows through a portion of the body causing a shock. The average adult
body is made up of 50-65% water. This makes it a good conductor of electricity. Burns are the most common
injury from electric shock, but exposure to electrical energy may result in devastating damage or death.
The minimum current a human can feel is thought to be about 1 milli ampere (mA), but
this is highly dependent on the frequency of the signal. The current may cause tissue damage
or fibrillation if it is sufficiently high. Death caused by an electric shock is referred to as electrocution. Generally, currents approaching 100 mA are lethal if they pass through sensitive portions of the body.Many variables determine what injuries may occur. These variables include the type of current (AC or DC), the amount of current (determined by the voltage of the source and the resistance of the tissues involved), and the pathway the electricity takes through the body. Low voltage electricity (less than 500 volts) does not normally cause significant injury to humans. Exposure to high voltage electricity (greater than 500 volts) has the potential to result in serious damage.Contact with electricity from a high-voltage wire or being struck by lightning needs emergency medical care. Contact with electricity from a low-voltage current needs emergency medical care if any signs or symptoms are present. A person who does not have any symptoms should still see a doctor to check for possible internal injuries.
Electric shock
Match questions and answers.
QUESTIONS 1
a. What does electric current do to muscle tissue?
b. What can electric current do to motor muscles (fingers, arms, legs)?
c. What can electric current do to heart and lungs?
d. Why should you use one hand while working on live power circuits? Which hand?
e. Why is water dangerous when working around electric power?
f. Why is metal jewelry dangerous to wear when working on electric circuits?
g. What kinds of tools are best for working on live power circuits?
h. What kind of immediate medical attention does an electric shock victim require?
i. What footwear is appropriate when working around electric power?
j. What footwear is not appropriate when working around electric power?
9
result in: risultare to strike (struck-struck): colpire tissue: tessuto
GlossAry
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