Over 7, entries. This new Dictionary provides definitions and explanations for mechanical engineering terms in the core areas of design, stress analysis. Here, we have various publication A Dictionary Of Mechanical Engineering ( Oxford Quick Reference) By. Tony Atkins, Marcel Escudier as well as collections to. Read eBook A Dictionary Of Mechanical Engineering (Oxford Quick Reference) By Tony Atkins, Marcel Escudier [KINDLE PDF. EBOOK EPUB].
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Oxford. Heilige Geeststraat B Leuven. HA| University Belgium. Press Council of the Institution of Mechanical Engineers, Making definitions. soundofheaven.info Harry James Potter . Oxford English . A good dictionary will show the stressed syllables. Listen to. Oxford English for Electrical and Mechanical Engineering. Home · Oxford Size Report. DOWNLOAD PDF Electrical engineering dictionary · Read more.
Technical reading Laser cutting Task 10 Engineers have to read sales literature describing the products and services of companies. The gas generated by the burning fuel expands rapidly, driving the piston down, both valves remaining closed. This has a very low boiling point: Polyester resin is hard and has good chemical and heat resistance. Technical reading Strain gauges Task 8 Read the text below to find the answers to these questions. This branch of engineering includes 6.
The other loop of the circuit passes to the radiators. Cold water from the radiators returns to the boiler. Use the statements in Task 4 to label the stages shown in this diagram of a heating system. Fira flwr Ground floor t 1 Language study Time clauses What is the relationship between these pairs of actions?
How can we link each pair to show this relationship? The water is heated. It reaches a pre-set temperature. It is pumped to a diverter valve. The gas control valve shuts off. We can show how actions are linked in time by using time clauses. We can use as to link two connected actions happening at the same time.
We can use until to link an action and the limit of that action. Note that until normally comes between the stages. We can use after to show that one action is followed by another action. We can use when to show that one action happens immediately after another. Note that when the time word comes h t in the sentence. Task 6 Link these sets of actions with appropriate time words.
Cold water passes through a heat exchanger in the boiler. The water becomes hotter and hotter. The water reaches a pre-set level. The water temperature reaches the pre-set level. A thermostat causes the gas control valve to shut off. The water is pumped to a diverter valve. The water goes to the hot water cylinder or the radiators.
Hot water passes through the inside of the hot water storage cylinder in a coil arrangement. Heat is transferred to the surrounding water. The hot water flows through the radiators.
The hot water loses heat. The water passes through the radiators. The water returns to the boiler. Word study Task 7 The words listed in the fust column of this table are common in descriptions of technical plant. They describe how substances are moved from one stage of the process to the next. Some of these words can be used for any substance: Write an X under Solids, Liquids, or Gases if the word on the left can be used to talk about them.
The k s t example has been done for you. Match each label to the correct warning. Task 2 List some of the potential dangers in your laboratory, workshop, or place of work. How is the risk of these hazards reduced? Task 3 Study the safety instructions from a workshop below, and then answer these questions.
I 1 2 Wear protective clothing at all times. Always wear eye protection whenoperating I lathes, cutters, and grinders and ensure the guard is in place.
Tools should be put away when not in use and I I any breakages and losses reported 1 6 Machines should be cleaned after use, Reading Understanding the writer'spurpose Knowing what the writer's purpose is, who the writer is, and who the intended readers are can help us to understand a text.
The safety instructions in Task 3 are clearly intended to encourage employees to be safety conscious and reduce the risk of accidents. The writer is perhaps a supervisor or the company safety officer, and the intended readers are machine operatives. Knowing these things can help us to work out the meaning of any part of the text we may not understand.
Task 4 Study the company document on safety on the next page, and then answer these questions. A written preliminary investigation will be completed by the end of the particular shift or business day on which the accident occurred. In no event should there be a delay of more than 24 hours. Failure to comply with this requirement may subject the immediate manager to disciplinary action up to and including discharge.
Without adequate accident investigation data the Company may be subjected to costs, claims, and legal action for which it has no defence. As a minimum, the preliminary accident investigation report will include the following: The employee who was injured and any employee s who witnessed the incident should be separately interviewed as soon as possible. A copy of the report must be submitted to the Manager - Human Resources for review.
Another copy of the report is to be retained for a period of not less than the injured employee's length of employment plus five 5 years. Task 5 Study this brief report of an accident. In which points does it not meet company policy on reporting accidents? Language study Making safety rules What are the differences in meaning, if any, between these statements?
We can make safety rules in these ways: Wear protective clothing. Do not wear loose-fitting clothing. Never wear loose-fitting clothing. Protective clothing should be worn.
Task 6 Study this list of unsafe environmental conditions hazards. Write safety rules to limit these hazards using the methods given above. We learnt how to mark reasons, results, and contrasts in our writing. What are the links between these ideas? Sentence 3 is an additional reason. We can mark the links between them like this: The accident happened because of the operator's carelessness. We use because of to introduce a reason which is a noun or noun phrase.
We use in addition and moreover to introduce an additional reason. Sentence 5 is an example to illustrate sentence 4. We can mark this in this way: Suitableprotection should be worn. Task 7 Show the links between these sets of ideas using appropriate linking woru. Workers' carelessness. It is important that all workers receive training in basic safety. Goggles must be worn for grinding and cutting. They prevent burns.
They reduce the danger of cuts. They prevent the feet getting caught in machinery. Dust can damage the lungs. Each year people are injured.
They refuse or forget to wear the right gear. Study this diagram of her invention. Discuss these questions in your group: Listening Task 2 m Now Listen to Lucy talking about her invention and career plans. As you listen, check your answers to Task 1. Task 3 rn Now listen again. Here are some of the things Lucy talks about.
Put them in the correct sequence. The first one has been done for you. Task 4 Now make notes on what Lucy says about the above topics. Task 5 Label the diagram in Task 1with these terms: Writing Describing and explaining Task 8 You are going to write a brief description and explanation of Lucy's invention. It will consist of two paragraphs. Paragraph I Use the labelled diagram in Task 1and the information from the tape to write a brief description of Lucy's invention.
Your description should answer these questions: Paragraph 2 The following steps explain how the swing works. Then use so and when to link them into a paragraph. The rope pulls the seat forwards. Repetition of these actions causes a swinging motion. The child puUs down on the handle. The seat swings back under the weight of the child.
The child releases the handle. Speaking practice Task 9 Work in pairs. A and B. Play the part of the interviewer. Base your questions on the topics in Task 3, and any other questions you may wish to add. Play the part of the swing inventor. Conduct the interview. Washing machine Task 1 Many items found in the home contain control systems. The washing machine is one of the most complex. List some of the factors the control system of a washing machine must handle.
This diagram may help you. They can also help you to understand the accompanying text. For this reason, it is helpful to try to understand any diagram before reading the text. Task 2 Study the diagram again. Try to explain the function of each of these items. For example, you can control the volume of a TV by using a remote control.
The building blocks of a control system are: Input -t Press bumn Signal is Volume on remote wntrol sent to TV is adjusted Theinput can be any movement or any change in the environment. The control may change the size of the output for example, adjustingthe sound of a N. Often this involves changing one kind of input into a different kind of output. For example, opening a l o window may set off a burglar alarm. Outputscan be of many kinds. An alarm system may ring a bell, flash lights, and send a telephone messageto the police.
Most control systems are closed loops. That means they incorporate a way of checking that the output is correct. In other 15 words, they have feedback. The thermostat in a central heating system Fig. These are door position, water level, water temperature, wash and spin times, and drum speeds.
YOU can see that this is quite a complex closed loop system using feedbackto keep a check on water level, water temperature, and 25 drum speeds. It receives and sends signals which control all the activities of the machine. It is alsc capable of diagnosing faults which may occur, stopping the program, and informing the service engineer what is wrong.
It i 30 small, dedicated computer which, like other computers, uses th language of logic. Fowler and M. When the door is closed, it completes an electrical circuit which heats up a heat-sensitive pellet. This expands as it gets hot, pushing a mechanical lock into place and closing a switch. The switch signals the control unit that the door is closed and locked. Read Texts 2 and 3. Read Texts 4 and 5.
Complete your section of the table opposite. Then exchange information with your partner to complete the whole table. Control factor Operating device Feedbackby 1 Door position heat-sensitive pellet switch 2 Water level 3 Water temperature 4 Wash and spin times - 5 Drumspeeds Text 2 Water Ieval When a wash program first starts it has to open the valves which allow the water in. There are usually two of these valves, one for hot water and one for cold. Each must be controlled separately depending on the water temperature needed forthat program.
The 5 valves are solenoid operated, i. The rising water level is checked by the water level sensor. This is a pressure sensor. The pressure of the air in the plastic tube rises as it is compressed by the rising water. The pressure sensor keeps the 10 control unit informed as to the Dressure reached and the control unit uses the information to decide when to close the water inlet valves. Water temperature The temperature sensor, a type of thermometer which fits inside the washer drum, measuresthe water temperature and signals it to the control unit.
The control unit compares it with the temperature nwded forthe program being used. If the water temperature is too 5 low, the control unit will switch on the heater.
The temperature sensor continues to check the temperature and keep the control unit informed. Once the correct temperature is reached, the control unit switches off the heater and moves on to the next stage of the program. Text 4 Clock The control unit includes a memorywhich tells it how long staae of a Droaram should last. The times mav be different he electronic clock built into the control unit keeps th memory of the control unit informed so that each stage of each 6 program is timed correctly.
Most machines use three different: The motor starts up slowly, then gradually increasesspeed. The spee sensor, a tachogenerator, keeps the control unit informed as to speed that has been reached. The control unit uses the informat to control the power to the motor and so controls the speed of the l o drum at all times.
Sensor Condition Control unit action Water level low open inlet valves level high enough Water temperature switch on heater high enough Drum speed decrease motor speed The conditions which the sensors report determine the action of the control unit.
We can link each condition and action like this: If the water level is low, the inlet valves are opened. Task 6 Write similar sentences for the other five conditions given. Now study this example: Sensor Condition Control unit action Door Door open Machine cannot start Door closed Machine can start We can link these conditions and actions as follows: We use unless when an action cannot or will not happen if a prior condition is not true.
In example 3. Unless means If We can rewrite 3 as: If the door is not closed, the machine cannot start. Task 7 Complete these sentences using Unless and your knowledge of engineering. Explain how it works by linking each pair of actions with appropriate time words. It opens the valves to allow the water in. The air in the plastic tube is compressed. The diaphragm moves upwards. The switch contacts are separated. The fill valves are closed.
Task 9 Join the following groups of statements to make longer sentences. Use the words printed in italics above each group. You may omit words and make whatever changes you think are necessary in the word order and punctuation of the sentences.
Join the sentences to make a paragraph. The temperature sensor is a type of thermometer. The temperature sensor signals the water temperature to the control unit. The temperature is needed for the programme being used. The control unit will switch on the heater. The temperature sensor keeps the control unit informed. The control unit switches off the heater. The control unit moves on to the next stage of the programme.
Task 3 Compare Fig. What differences can you note? Write your answers in this table. Conventional Fig. The frame to the pedals. They are called 'triathlon' bars shown is a low profile machine. Dave Scon. I Fig. Then study Fig. Improvement Reason Disc wheels Combined gear change and brake levers Carbon fibre frame Clipless pedals Precision-engineered aluminium- alloy or titanium gears Aerodynamic handlebars Reading Prediction Task 5 Study this extract from the text you are going to read.
Bicycles, and especially racing bicycles, have much in common with aircraft: What similarities between racing bicycles and aircraft do you think the text win cover?
Note your predictions. Task 6 Read this text to check your answers to Task 5. But in the past 10 years there have been more changes than during any other decade. Bicycles, and especially racing bicycles, have much in common 5 with aircraft: So, much of the technology used in aerospace has found its way into racing bicycles.
It must be strong, light, flexible enough to absorb bumps, but not so much tbat itwastes the enerav the rider transmits by pedalling. I Bicycle frame designers share many aims with aircraft engineers, who must design wings which are strong, light, aerodynamic, and 5 efficient at converting engine power into lift.
Yet the wings must be flexible enough to absorb turbulence without wasting the engine's thrust. Therefore, the modern bicycle frame and aircraft wing share both materials and design features.
Many racing bicycle frames which consist of tubes joined together are made from aluminium 1 alloys similar to those used in aviation. It is no surprise that some racing bicycleframesare now manufactured from the same materials. Its designer, Frank Kirk, formerly worked i n h Language study Describing reasons We can describe the reasons for an improvement or design change in a number of ways.
Study this example: How many ways do you know to link an improvement and the reason for it; Try to complete this sentence by adding the reason given. New racing bicycles have disc wheels to reduce wind resistance. Another simple way is to use a linking word. You studied this in Unit 5. A more difficult way is to use so that which must be followed by a clause. New racing bicycles have disc wheels so that wind resistance is reduced. Task 7 Link each improvement and reason in Task 4 using the methods given above.
Writing Describing contrast In engineering, it is often necessary to compare and contrast different proposals, solutions to problems, and developments.
In this unit we will focus on contrast -describing differences. We can show differences in a table like this: Conventional Improved bicycle Spoked wheels Disc wheels Gear lever on the frame Combined gear change and brake levers Tubular aluminium-alloy frame Carbon fibre frame Pedals with toe-clips Clipless pedals Steel gears Precision-engineered titanium gears Ordinary handlebars Aerodynamic handlebars We can describe differences using: The new bicycle is lighter than the old. The new bicycle is more aerodynamic than the old.
Titanium geurs can be changed moreeasily. On new bicycles the gear and brake lever are combined, whereas on old ones, the gear lever is on the frame. Old bicycles have spoked wheels. In contrast, the new bicycle has disc wheels. Unlike the conventional bicycle, the new bicycle has a carbonfibreframe.
The new bicycle is differentfrom the conventional one in that the gears ure made oftitanium. Note that these expressions assume that the reader is familiar with the materials used in the conventional bicycle, which are not mentioned.
Task 8 Describe the differences between a conventional and an improved bicycle using the information in the table above and appropriate expressions from the list provided. Word study Properties of materials Study these examples of adjective and noun pairs for describing the propertien of materials. Adjective Noun wind resistance elastic plasticity tough soft rigid wear-resistant brittleness hard Speaking practice Task 10 Work in pairs.
Your task is to explain to your partner how to adjust the distance between the saddle and the handlebars of a racing bicycle. Use the text and diagrams on pages to help you. Your task is to explain to your partner how to adjust the height and tilt of the handlebars of a racing bicycle.
Technical reading Gear systems a Fig. I Driven sprocket has 15 Number of teeth on driver sprocket ,v-. Task 11 Calculate the gear ratios of a bicycle with the system shown in Fig. It has a double chain-wheel and five driven sprockets on the rear wheel but only the combinations shown below are recommended. You may need a calculator. List any applications you know for lasers.
In the s. Nowadays, they are usedto identify targets. But apart from military uses, they have many applications in engineering D communications, medicine, and the arts. In engineering, powerful laser beams can be focused on a small area. These beamscan heat, melt, or vaporize material in a very precise way.
They can be used for drilling diamonds, cuning complexshapes in materials from plasticsto steel, for spot welding 15 and for surfacing techniques, such as hardening aircraft engine turbine blades.
Laser beams can also be usedto measure and align uctures. Lasers can I also be used for information recording and reading.
Compact discs are read by lasers. I In medicine, laserbeams can traal damagedtissue in a fraction of a second without harming healthy tissue. They can be used in very precise eye operations. Inthe arts, laserscan provide fantastic displays of light.
Pop concerts are often accompanied by laserdisplays. Task 3 Complete this table of laser applications using information from the text opposite. You may also add any applications you know of which are not included in the text.
Task 4 Describe the applications of lasers using the information in your table in Task 3 and the structures given above. Rewrite each compound to show the relationship. Consider these stages in the operation of a washing machine. The drum is filled with water.
The water is heated to the right temperature. Soap is added. The drum is rotated slowly. The dirty water is pumped out. Clean water is added. The drum is rotated much faster and the water pumped out. The clean clothes are removed. Instead of numbers, we can show the correct order using sequence words.
First the drum is filled with water. Then the water is heated to the right temperature. Next soap is added. After that, the drum is rotated slowly. Next the d i i y water is pumped out. Then clean water is added. After that, the drum is rotated much faster and the water pumped out. Finally, the clean clothes are removed. Task 7 Study this diagram. It shows an extruder for forming plastic pipes.
Describe the extruder. The hot plastic is forced through the die to form a continuous length of pipe. The plastic granules are mixed and placed in the hopper. The pipe is cooled and cut to suitable lengths.
The plastic melts, Task 9 Describe the correct order using sequence words. Add to your description of the process your description of the extruder from Task 7. Form your text into a paragraph. Technical reading Laser cutting Task 10 Engineers have to read sales literature describing the products and services of companies.
Read the following sales literature to answer these questions: By having to restrict designs to suit manufacturing processes?
By the difficulty and high cost of producing accurate prototypes? By the high cost and lengthy lead times associated with press tools? By the high stock levels necessitated by minimum batch sizes? If your answer to any of the above is yes T h e Process ITke mriah Lasertechnology is not 'he laser is suitable for cutting: Plastics, wood, fibreglass, andalmost any you care to mention!
Taking light and passi itthrough a series of lenses makes the light Carbon Steel- up source so greatthat its Stainless Steel- u power density is several 'Ptastics-upto 40 million times that of the Wood - up to 40 mm - sun this laser energy is Rubber - up to 40 mrn then used to cut almost Table movement mm x rnm any material. The light is directed down shortlead time I to produce accurate I Source: Listening Task 2 Listen to Part 1 ofthe intervieiv. Task 3 El Listen to Part 2 of the interview and answer these questions.
L How many technicians are in his section? Task 4 El Listen to Part 3 of the interview and answer these questions. Task 5 El Listen to the interview again and complete the gaps in this record of Alistair's work experience.
Period Type of company Product Jobtitle 2 years Automation technician years Telephone exchange months Instrument makers Student placement Speaking practice Talking about specijcations Task 6 Work in pairs.
Some of the design specifications for your drawing are missing. Complete them with help from your partner. Before you start, make sure you know how to say these abbreviations and expressions in full: Your specifications are on page It explains how a refrigerator works.
In your group try to work out the function of each of the numbered components using the information in the diagram. Your purpose is to find out how they operate.
Read the first paragraph of the text below. Underline any words which are unfamiliar to you. Refrigeration Dreserves food by lowering its temperature. It slows down the growth and reproduction of micro-organisms such as bacteria and the action of enzymes which cause food to rot. You may have underlined words like micro-organisms, bacteria, or enzymes.
These are words which are uncommon in engineering. Before you look them up in a dictionary or try to find translations in your own language, think! Do you need to know the meaning of these words to understand how refrigerators operate? You can ignore unfamiliar words which do not help you to achieve your reading purpose. Task 2 Now read the text to check your explanation of how a refrigerator works. Ignore any unfamiliar words which will not help you to achieve this purpose.
Refrigeration is based on three principles. Firstly, if a liquid is s heated, it changesto a gasorvapour. When this gas is cooleQjt changes badc into a liquid. Secondly, if a gas is allowed to expnnd, it cools dawn. Thirdly, lowering the pressure around a liquid helps it to boil. To Keep the refrigerator at a constant fow temperature, heal l o be transferred from the inside of the cabinet tome outside. It is circulated around the fridr; where it undergoes changes in pressure and temperature a chenges from a liquid to a gas and backagain.
One common refrigerant is a compound of carbon, chlorine, and i s fluorine known as R This has a very low boiling point: The refrigeration process begins inthe Compressor. This m compresses the gas so that it heats up.
Itthen pumps the gas intcr - I condenser, a long tube in the shape of a zigzag. As the warm gas passesthrough the condenser, it heats the surroundings and cools down. By the time it leevesthe condenser, it hascondansed back into a liquid.
This prevents liquid from leaving the condenser too quickly, and keeps it at a high pressure. The liquid o turns to vapour, which expands and cools. The cold vapour absorbs heat from the fridge.
Language study Principles and laws Study these extracts from the text above. What kind of statements are they? Each consists of an action followed by a result. Action Result a liquid is heated it changes to a gas or vapour These statements are principles.
They describe things in science and engineering which are always true. The action is always followed by the same result. Principles have this form: Link each action in column A with a result from column B to describe an important engineering principle.
Complete the blanks. You have studied these words in this and earlier units. Use a dictionary to check any spellings which you are not certain about. A Verbs B Nouns For example: It describes the refrigeration process.
In Unit 13 we learnt that when we write about a process, we have to: This compresses the gas explanation so that it heats up. In this unit we will study ways to locate the stages. Put these stages in the refrigeration process in the correct sequence with the help of the diagram above. The liquid turns to vapourin the evaporator.
The gas cools down in the condenser. The warm gaspasses through the condenser, whereit heats the surroundings and cools down. First the gas passes through the condenser Make your statements into a paragraph adding extra information from the text in Task 2 if you wish. Then compare your paragraph with paragraphs 6. Task 1 Complete this table of common quantities and forces to be measured in engineering, the units in which they are measured, and the instruments you use to measure them.
What alternatives are there? If you cannot name the instruments, draw them. Task 3 What do you think are the advantages of electronic scales over mechanical scales? Reading 1 Meaning from context Read the first two paragraphs of this text and try to fill in the missing words.
More than one answer is possible for some of the blanks.
Then check your answer to Task 3 using the completed text. Electronic scales para The electronic kitchen scale takes a larger load and is 1 accurate than its mechanical counterpart. Whereas a scale may have a capacity of about 3kg, b r o k e n 4 2 5g units, the electronic scale can a load of to 5kg broken into units of 5g or even 2g. The scale by converting the load increase on its platform weighing area into a weight reading 9 the liquid crystal display LCD.
It is controlled '" microprocessor and can therefore 'I from ounces to grams at the touch of a button. The compact internal components also make it small and 'l to store. Reading 2 Comparing sources When we read, we may wish to look at more than one source of information on a topic to: Task 5 Study this diagram of electronic scales and complete the notes below.
The change in voltage. Task 6 Scan this text to find information on the load cell, the strain gauge, and the circuit board. Note any information in the text which is new, i. The load cell, an aluminium alloy beam, eliminates the need for springs, cogs, or other moving parts which can wear, break, or cause inaccuracy in mechanical scales.
The strain gauge consists of a small piece of metal foil which detects any bending of the beam. A controlled input voltage is supplied to the strain gauge from a battery-poweredcircuit. When a load is placed on the platform, it causes the load cell to l o bend very slightly.
This, in turn, causes a change in strain, which triggers a change in the electrical resistance of the strain gauge. As the resistance changes, so does the output voltage from the strain gauge. In short, the change in voltage across the strain gauge is proportional to the load on the platform.
Thevoltage from the gauge is small and has to be amplified and 15 then converted into a digital signal. This signal is fed to a specially programmed microprocessor, which converts it into a weight readina. This is disolaved on the LCD. The disolav will automatically switch i f f afew minutes afterweighing isfinished, zo thereby saving battery power.
Education Guardian Language study Cause and effect, 1 Study these actions. What is the relationship between them? In each case, the first action is the cause and the second action is the effect. We can link a cause and effect like this: In these examples, both the cause and the effect are clauses - they contain a subject and a verb.
The strain gauge is stretched. An increase in electrical resistance. The effect is a noun phrase. We can link cause and effect l i e this: The strain gauge is stretched, which causes an increase in electrical resistance.
In Unit 22 wc will study othcr ways to link a cause and an effect. Task 7 The diagram below is a cause and effect chain which explains how a strain gauge works. Each arrow shows a cause and effect link. Match these actions with the correct boxes in the diagram. An increase in resistance. A load is placed on the scale. A drop in voltage across the gauge.
The load cell bends very slightly. They become longer and thinner. The strain gauge conductors stretch. The strain gauge bends. Technical reading Strain gauges Task 8 Read the text below to find the answers to these questions. What principle do strain gauges operate on?
Why is it an advantage to have a long length of conductor formed into many rows in a strain gauge? If you want to measure strain in a member, how do you position the strain gauge? Why is an amplifier necessary? Why is a dummy gauge included in the circuit?
What is the function of VR2; Why would you adjust the output to exactly zero? In the circuit shown, how is the amplifier output displayed; as: By arrangingthe wire in tightly packed rows, quite long lengths can befitted on to a small pad Fig. Modem strain gaugesare made not of wire, but by etching a pattern into metal foil which is stuck to a polyester backing Fig. Its active axis is fixed along the direction in which you want to measurethe strain.
Movements on the passive axis will have no real effect on it. The gauge must then be connected to an electronic circuit. The i s resistance of the gauge iscompared with the resistance of fixed value resistors in the circuit. Any differences in resistance are converted into voltage differences. These verv small changes in v e are amplified befori i g dis Fig. This 20 comoensates for any changes in the resistance of the active gauge caused by temperathe changes.
The active and dummy gauges form part of the Wheatstone bridge. The three variable resistors i n the circuit each allow different adjustmentsto be made. VR1 allows you to 'balance'the bridge, getting the resistances exactly equal.
VR2 allows you to adjust the I 'gain' of the amplifier, in other words, how much the voltage is amplified. By adjusting VR3 the output can be adjusted to exactly zero before a load is applied to the member being tested. In practice, strain gauges tend to be used i n pairs or groups, often measuring the strain in various parts of a structure at the same i time.
When used like this they are often linked to a computer rathe than a series of display meters. The computer keeps a constant checkon the outputs from each of the strain gauges, making sure that no pan of the structure is being loaded beyond normal limits. Horsley, 'Control Systems in the Home'. Reading Reading diagrams Task 2 Study the diagram below of a portable generator. Answer these questions using the diagram and your own knowledge of engineering.
Stator windings 0 I Exhaust in which current is generated Fig. You will not find complete answers to all of the questions. Portable grnerator Although most electricity comes from power stations, power can also be generated by far smaller means. Nowadays, electricity generatorscan be small enough to hold inthe hand. Portable generators are made up of two main parts: The engine shown Fig.
It is started by pulling a cord. This creates a spark inside which ignites the fuel mixture. In a typical four-stroke engine, when the piston descends, the air to inlet valve opens and a mixture of air and petrol issucked in through a carburettor. The valve closes, the piston rises on the compression stroke and a sparkwithin the upper chamber ignitesthe mixture. This mini- explosion pushesthe piston backdown, and as it rises again the 15 fumesformed by the ignition are forced outthrough the exhaust valve.
This cycle is repeated many times per second. The moving piston makes the crankshaft rotate at great speed. The crankshaft extends directly to an alternator, which consists oi 'o two main sets of windings -coils of insulated copper wire wound closely around an iron core. One set, called stator windings, is in i fixed position and shaped like a broad ring. The other set, the armature windings, is wound on the rotorwhich is fixed to the rotating crankshaft. The rotor makes about 3, revolutions per 25 minute.
The rotor is magnetized and as it spins round, electricitv is generated in tha stator windings through thepr- of electromagnetic induction. The etectric current is fedt o the output rminals or sockets. Larger versions provide emergency power to hospitals and factories. Task 4 Study this text on the four-stroke cycle. Then label each stroke correctly in Fig.
The pisi wends on the compression stroke with both valvesclosed. IBU tgnition takes place at the top of the stroke. The pwver or expansion stroke 5 follows. The gas generated by the burning fuel expands rapidly, driving the piston down, both valves remaining closed.
The cycle is completed by the exhaust stroke, as the piston ascends once more, forcing the products of combustion out through the exhaust valve. The cycle then repeats itself. Carburettor Fuel inlet valve I d Fig. What is the link between each pair? There are two links between the actions: They happen at the same time. We can show this using As see Unit 8.
One is a cause and the other an effect. The gas expands. This drives the piston down. The piston ascends. This forces the products of combustion out. We can show both the time link and the cause and effect link like this: Task 5 Link these actions in the same way. Cause Effect The piston moves down the cylinder. This creates a partial vacuum. The piston creates a vacuum, This draws in fuel from the carburettor. The piston moves up the cylinder.
This compresses the mixture. The gas expands quickly. This pushes the piston down. The piston moves up and down. This rotates the crankshaft. The crankshaft spins round. This turns the rotor at 3, rpm. The armature of the alternator rotates. This induces a current in the stator windings.
The alternator runs at a steady 3. This generates around watts. You can change your ad preferences anytime. Upcoming SlideShare. Like this presentation? Why not share! An annual anal Embed Size px.
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Book details Author: Tony Atkins Pages: Oxford University Press Language: English ISBN