M. Ibbotson - Professional english in use engineering (794233), страница 27
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Circuit breakers also allow circuits to be switched off manually, toisolate them (switch them off safely) -for example, before maintenance work.Note: The equipment in switchboards is often called switchgear.-Printed and integrated circuitsThe circuits in electrical appliances are often printed circuits, on printed circuit boards (PCBs).These are populated with (fitted with) electrical components.
Many appliances also containsmall, complex integrated circuits- often called microchips (or chips)- made from siliconwafers (very thin pieces of silicon). They act as semiconductors, which can be positivelycharged at certain points on their surface and negatively charged at other points.This principle is used to make very small circuits.-Electrical and electronic componentsThere are many types of electrical and electronic components. These can be used individuallyor combined with other components to perform different tasks. For example:•Sensors or detectors can sense or detect levels of- or changes in - values such astemperature, pressure and light.•Control systems use feedback from sensors to control devices automatically.
For example,mechanical devices such as water valves may be moved or adjusted by servomechanismselectrically powered mechanisms that are controlled automatically by signals ('messages')from sensors.•Logic gates are widely used in control systems. They send signals, in the form of lowvoltages, to other devices. An output signal from the logic gate is switched on or off,depending on the input signals it receives.Notes: The term electronic, rather than electrical, generally describes small but often very complexcircuits and components that operate at a low voltage.See Appendix XII on page 114 for more on electrical and electronic components and logicgates, and Appendix XIII on page 118 for more on sensors and detectors.96Professional English in Use Engineering45.1Make word combinations with circuit using words from A and B opposite.
Then match thecombin ations with the descriptions (1- 6) below.a································a .............................. ..a ............................... .a ............................... .a .............................. ..an .............................. ..1 a circuit containing one or more sockets2 a simple circuit where all the components are placed one after the other along the sameconductor3 a microchip - a very small, often complex circuit4 what happens if live and neutral conductors touch while a current is flowing, and there isno component or appliance between them5 a circuit which allows different comp onents to be controlled independently by separateswitches6 a circuit that can be populated with a large n umber of components45.2Comp lete the task from an engineering textbook. Sometimes more than one word is possible.Look at Band C opposite and Appendix XIII on page 118 to help you.In an experiment, the lights in a room are connected to two types of electronic(1) ................................
. The fi rst is an occupancy sensor, which will (2) ................................ themovement of a person entering the room, and the second is some kind of photosensor, whichcan determine whether it's daylight or dark. These two devices are connected to an AND gate- a (3) ................................................................ that will produce an output current only if it receivestwo input currents - in this case, from both the occupancy senso r and the photosensor.Therefore, a (4) ................................ will be sent to the light switch to (5) ...............................
................................. the lights only if a person enters the room and if it's dark.However, fo r this system to work, we are assuming that the type of photosensor used will beone which is designed to produce a current in the dark, and which will then (6) .............................. ..................................
as soon as daylight appears. But such a sensor may be designed to work inthe opposite way - producing a current when it detects daylight and no current in the dark.This would cause an obvious problem. In this case, what type of logic gate could be placedbetween the photosensor and the AND gate in order to solve the problem?45.3Can you answer the question in the text in 45 .2? Look at Appendix XIII on page 118 to help you.A printed circuit boardov~rAn integrated circuit on a microchipl.f-o t:fou D~Think of a device or installation you're familiar with which is automatically controlled, anddescribe its control systems.
What kinds of sensor are used? How does the control systemreact to different signals from the sensors?Professional English in Use Engineering97Three-dimensional drawingsAn oblique projection shows an object withone of its faces at the front . The 3D shapeof the object is shown by lines at 45 degreesfrom the horizontal.An oblique projectionAn isometric projection shows an object withone of its corners at the front. The 3D shapeof the object is shown by lines at 30 degreesfrom the horizontal.An isometric projectionAn exploded view shows an assembly with its components spaced out, to show how thecomponents fit together.An exploded view showing part of a lawn mower98Professional English in Use EngineeringShapesThe nouns and adj ectives below can be used to describe the shapes of components andassemblies.20 shapes30 shapesNounAdjectivesquaresquarerectanglerectangulartriangletriangular6hexagonhexagonaloctagonoctagonalpentagonpentagonalcirclecircularsemicirclesemicircularspiralspiralNounAdjectivecubecubic[jlcylindercylindrical&?tubetubular0spherespherical000hemispherehemisphericaldomedome-shapedconeconical Icone-shapedpyramidpyramidal Ipyramid-shapedhelixhelical~wedgewedge-shaped60DD0~64>Notes: The noun cylinder is often used to describe a hollow cylinder that is enclosed - for example,piston cylinders (in engines) or gas cylinders (gas containers) .
A hollow cylinder that is openat both ends is generally called a tube.The difference between a dome and a hemisphere is that a dome is hollow (not solid), and isnot necessarily perfectly hemispherical.In everyday English, spiral is often used to describe a helix- for example, a spiral staircase.The helical groove on a screw, bolt or nut is called a thread .Professional English in Use Engineering99Units of measurementSl base unitsThe International System of Units - abbreviated as SI from the French name, SystemeInternational d'Unites - is the most widely used system of measurements. Some SI units, suchas metres and kilograms, are often described as metric units.
The seven base units of the SIsystem are shown in the table below.QuantityUnitAbbreviationlengthmetremmasskilogramkgtimesecondselectric currentampereAthermodynamic temperaturekelvinKamount of substancemolemolluminous intensitycandelacdNote: 0 kelvin (K) = -273 degrees Celsius (OC). 0 K is the lowest possible temperature- often calledabsolute zero.Sl derived unitsSI derived units are related to the SI base units. They include a wide range of specific units.The table below lists SI derived units commonly used in engineering.QuantitylengthUnitAbbreviationNotesmillimetremm1mm =0.001mcentimetreem1cm =0.01mkilometrekmsquare metrem2square millimetremm2cubic metrem3cubic centimetrecclitre1gramgtonneTnewtonN= 1,000m1m2 = 1m x 1m1mm2 = 1mm x 1mm1m3 = 1m x 1m x 1m1 cc = 1 em x 1 em x 1 em11 =0.001m31g =0.001kg1 T = 1,000kg1 N = the force exerted by theareavolumevolume of liquidmassforcedensitypressure andstressI 001kmearth's gravity on a mass ofapproximately 0.1 kgkilograms percubic metrekg/m 3If a volume of 1m3 of material hasa mass of 1 kg its density = 1 kg/m 3.PascalPa1PaProfessional English in Use Engineering= 1N/m2UnitAbbreviationNotesmetres per secondm/sIf an object travels 1 metre in 1second, its speed or velocity is 1 m/s.kilometres perhourkmlhIf an object travels 1 kilometre in 1hour, its speed or velocity is 1 km/h.metres per secondsquaredm/s 2If the speed or velocity of an objectincreases by 1 m/s every second, ithas a rate of acceleration of 1 m/s 2 •newton metresNm1 Nm = 1 N of force exerted at adistance of 1 m from a fulcrum oraxis of rotationdegree CelsiusocTemperature in oc = temperaturein kelvin (K) + 273 (see note underbase units above)frequencyhertzHz1 Hz = 1 cycle per secondangularmovementradianrad2rr rad = 360 degreesradians persecondrad/sIf an object rotates through 1 radianin 1 second, its angular velocity is1rad/s.radians persecond squaredrad/s 2If the angular velocity of an objectrevolutions perminuterpmIf a revolving shaft or wheel makes1,000 rotations every minute, itsrotational velocity is 1,000 rpm.jouleJIf a force of 1 N is needed to keepQuantityspeed/velocityaccelerationmoments andtorquetern peratureangular velocityangularaccelerationrotationalvelocityincreases by 1 rad/s every second, itsangular acceleration is 1 rad/s 2 •an object moving, the work requiredto move the object over 1m = 1 J.energypowerwattw}/(kg C)specific heatcapacityjoules perkilogram degreesCelsius1W=1J/s0If 1 J of energy is needed to raise thetemperature of 1 kg of a substanceby 1 oc, its specific heat capacity is1}/(kg C).0latent heat offusion andlatent heat ofvaporizationjoules perkilogram]!kgIf 1 J of energy is needed to changethe state of 1 kg of a substance, itslatent heat of fusion/vaporization is1Jikg.Professional English in Use Engineering10151 units for electricityUnitAbbreviationelectromotive forcevoltvelectrical resistanceohmelectrical conductancesiemenselectrical chargecoulombnsccapacitancefaradFinductancehenryHmagnetic fluxweberWbmagnetic flux densityteslaTUnit prefixesThe prefixes below can be written in front of units to multiply them or divide them by aspecific number.
For example, 1 milliamp (rnA) = 0.001 amps, and 1 kilonewton (kN) =1,000 newtons.PrefixAbbreviationMultiplication factorteraTX1,000,000,000,000gigaGX1,000,000,000megaMX1,000,000kilokX1,000hectohX100dekadaX10decidX0.1centicX0.01millimX0.001microj.lX0.000001nanonX0.000000001piCOpX0.000000000001Common UK Imperial, US Customary and other non-51 unitsQuantitylengthI 02UnitAbbreviationinch (plural, inches)infoot (plural, feet)ft12 in1 ft = 304.8 mmyardyd3ft1 yd = 914.4mmstatute mile (or mile)(no standard)5,280 ft1 statute mile =1,609.344mProfessional English in Use EngineeringDescription51 equivalent1 in= 25.4mmQuantityUnitAbbreviationDescription51 equivalentnautical mile (usedin aviation andshipping)(no standard)6,076.115 ftlength1 nautical mile =1,852 mmiles per hour{statute miles perhour)mphmiles travelledin 1 hour1 mph=1.
609344kmlhknot (nautical milesper ho ur)kn I kt(s)nautical milestravelled in1 hourlkt = 1.852kmlhounce (internationalavoirdupois ounce)ozpound (internationalavoirdupois pound )lbpound-force persquare inchpstspeed/velocity1 oz = 0.02 835 kgmasspressure andstressbaratmosphericpressurel ib=0.45359237 kg1 psi=6,894.76Paapproximatelyequal toatmosphericpressure at sealevel1 bar =lOO,OOOPafoot-pound force(foot pounds)ft.lbmoment of libforce exertedat 1 ft from ashaft's axis ofrotationapprox .1.355 81 Nmmechanicalhorsepowerhpa historic unitapprox. 745 .7 Wmetric horsepowerhpa historic unitapprox. 735.5 Wtorqueengine power16 ozNotes: In British industry, 51 units- not imperial units- are used .In aviation and shipping, nautical miles (distance), knots (speed) and feet (altitude -foraircraft) are used as the international standard.Engine horsepower is usually measured in brake horsepower (bhp).
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