engineering studies - School Curriculum and Standards Authority
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1. ENGINEERING STUDIES 80 STAGE 3 Additional working space STAGE 3 81 ENGINEERING STUDIES Additional working space ENGINEERING STUDIES 82 STAGE 3 Additional working space STAGE 3 83 ENGINEERING STUDIES See next page ACKNOWLEDGEMENTS Question 13 Text adapted from Berrill T amp Blair A 2007 Solar water heater training course Installer and user manual Melbourne Australian Business Council for Sustainable Energy Retrieved March 2012 from www cleanenergycouncil org au resourcecentre Consumer Info SWHguide html This examination paper apart from any third party copyright material contained in it may be freely copied or communicated on an intranet for non commercial purposes in educational institutions provided that it is not changed and that the School Curriculum and Standards Authority is acknowledged as the copyright ow2. 2 0m Cross section Elevation The material and loading properties are Component Weight Load Cantilever beam 200 kg m Cross beam 50 kg m Decking 900 kg m People 500 kg m You can assume that each cantilevered beam carries the loads from a 2 0 m length of balcony Also each cross beam carries a share of the loads imposed from the decking and the people standing on the balcony from that part of the decking equidistant from each adjacent cross beam a Show that the load imposed on the balcony by the people and the weight of the decking is about 5341 N m 3 marks See next page MECHANICAL 49 ENGINEERING STUDIES STAGE 3 b Show that the loads imposed by the four cross beams that support the decking and the people on the balcony on the cantilever beam are approximately as follows 5 marks 11662 N 11662N See next page ENGINEERING STUDIES 50 MECHANICAL STAGE 3 Question 40 continued c Sketch the shear force and bending moment diagrams for the cantilever beam on the following axes Calculate the key numeric values to fully define the shape of the diagrams and show these values on the diagrams 17 marks SF J E S SS SS S BM See next page MECHANICAL 51 ENGINEERING STUDIES STAGE 3 Question 41 25 marks The diagram below shows a schematic representation of a railway wagon on a track approaching an energy
3. ELECTRONIC ELECTRICAL 63 ENGINEERING STUDIES STAGE 3 b Given that the source voltage is set to a value such that the resistor R is dissipating 100 mW of power calculate the values for the voltage V the current 7 and the source voltage V Show all workings i Voltage V 2 marks ii Current 4 marks iii Source voltage Vs 4 marks See next page ENGINEERING STUDIES 64 ELECTRONIC ELECTRICAL STAGE 3 Question 53 continued c Consider the following two separate scenarios i If the resistor R was replaced by another resistor of lesser resistance value while all other circuit elements remained unchanged how would this affect the total resistance R and the current Tick the appropriate boxes below and provide a reason for each 4 marks The total resistance R would e increase decrease remain unchanged Reason The current would e increase decrease remain unchanged Reason See next page ELECTRONIC ELECTRICAL c ii 65 ENGINEERING STUDIES STAGE 3 If the source voltage was increased in value while all other circuit elements remained unchanged how would this affect the total resistance R and the current Tick the appropriate boxes below There is no need to show your workings The total resistance R would increase e decr
4. absorbing buffer stop The railway wagon weighs 5000 kg when fully loaded and is potentially moving at up to 20 km h If the brakes on the wagon fail the buffer stop is intended to bring the wagon to rest without any major damage The buffer stop is made up of a compressible ram with a very large spring contained in a large block of concrete The ram has a linearly elastic response to an imposed force The characteristics of the ram are as shown in the graph below 250 Force kN 500 Change in length mm The change in length horizontal axis is a measure of how much the ram moves and force vertical axis is the force required to make the movement The slope of this graph is called the stiffness of the ram You can assume that the buffer stop is heavy enough not to move when struck by the wagon See next page ENGINEERING STUDIES 52 MECHANICAL STAGE 3 Question 41 continued a Explain the difference between potential and kinetic energy and describe the changes in these energy types you would expect to occur when the wagon hits the buffer stop 5 marks Potential energy Kinetic energy Changes b Show that the kinetic energy contained in the wagon when it is moving at 20 km his close to 77 160 N m 3 marks See next page MECHANICAL 53 ENGINEERING STUDIES STAGE 3 c When the wagon hits the ram the spring contracts and the wagon gradually come
5. b results only from the self weight of the beam c is applied uniformly along a part of the beam d is applied at the mid and quarter points of the span of the beam The SI unit used to describe energy is the joule An alternative is a newton metre b newton per metre c watt per metre d watt If the factor of safety for the design of steel bolts is 1 5 and it is known that a 10 mm diameter bolt will fail at a load of 100 kN you would expect the diameter of a bolt to safely carry 100 kN will be at least a 15 2 mm b 14 1 mm c 12 2 mm d 11 4 mm The units of stress for a member of a structure with a tensile force in it are a kg m b kg m s c kg m s d kg m s The following diagram shows a force F acting on a rectangular object The moment of the force F about a point P is best described by a Fxa b Fxb c Fxe d Fx a b See next page MECHANICAL 43 ENGINEERING STUDIES STAGE 3 38 If a ball with mass of 0 1 kg is thrown upward and reaches a height of 20 m above ground before falling back to the ground its potential energy when at its highest point is closest to a 19 6 J b 30 4 J c 50 0 J d 69 6 J See next page ENGINEERING STUDIES 44 MECHANICAL STAGE 3 Part B Extended answer 55 105 Marks This part has four 4 questions Answer all questions Write your answers in the spaces provided Spare pages are included at the end
6. been programmed to cater for a power interruption then the a program resumes at the last instruction being executed before the power was switched off b processor restarts the program at the first instruction c microprocessor must be reprogrammed because its ROM has been erased d result is unpredictable See next page ENGINEERING STUDIES 20 SYSTEMS AND CONTROL STAGE 3 18 19 20 2l 22 In a rack and pinion gear system if the pinion gear has a circumference of 12 cm and the length of the rack is 288 cm how far will the rack move if the pinion is rotated 5 times a 2 4 cm b 12 cm c 24 cm d 60 cm In a typical vehicle power steering system the driver turns the steering wheel which in turn varies the hydraulic pressure applied to the drive of the front wheel rack and pinion steering linkage The system is an example of a closed loop control system a only when the driver is considered to be part of the control loop b only when the driver is not part of the control loop c irrespective of whether the driver is part of the loop d only when the vehicle is in motion If an AC voltage is applied to a diode the diode will block a the positive component of the signal b the positive or negative component of the signal depending on how the diode is wired c the negative component of the signal d neither the positive or negative components of the signal as its purpose is to sm
7. comply with the Guidelines 1 mark Referring to Clause 2 10 of the Guidelines what could happen if it was possible for the driver to remove the ignition key no matter what position it was in Explain your answer 2 marks Result of action Explanation An electric drive system is being fitted to a vehicle that normally has four passenger seats The owner advises you that they do not want to use the two rear seats after the conversion if it means that more batteries can be installed in the vehicle to increase the range You note that the approved loaded weight for the unmodified vehicle would have been based on four passengers and their luggage Assuming that the batteries each weigh 6 kg calculate how many could be fitted in place of the rear passengers and their luggage allowances Show all workings 4 marks End of Section One See next page ENGINEERING STUDIES Section Two Specialist fields Candidates are required to choose one of the following options according to which specialist field they studied in 2012 18 Tick one of the boxes below to indicate your choice of option 65 115 Marks Specialist field v Question numbers Pages Systems and Control 15 28 19 39 Mechanical 29 42 41 57 Electronic Electrical 43 56 59 78 Now turn to the relevant pages and answer the questions for the specialist field you have selected See nex
8. deducted for incorrect answers No marks will be given if more than one answer is completed for any question Section One Part B Write answers in this Question Answer Booklet Answer only three 3 questions Section Two Part B You must choose to answer only one 1 of the specialist sections Write answers in this Question Answer Booklet All questions must be answered 3 You must be careful to confine your responses to the specific questions asked and to follow any instructions that are specific to a particular question 4 Spare pages are included at the end of this booklet They can be used for planning your responses and or as additional space if required to continue an answer e Planning If you use the spare pages for planning indicate this clearly at the top of the page e Continuing an answer If you need to use the space to continue an answer indicate in the original answer space where the answer is continued i e give the page number Fill in the number of the question s that you are continuing to answer at the top of the page 5 The Document Booklet and Data Book are not handed in with your Question Answer Booklet See next page CORE CONTENT 3 ENGINEERING STUDIES STAGE 3 Section One Core content 35 45 Marks This section has two 2 parts PartA Multiple choice Answer all questions PartB Extended answer Answer three 3 questions Suggested working time 60 minutes Part A Multiple choice 10 10 Mark
9. how a Pulse Width Modulation PWM controller varies the speed of a typical DC electric motor 3 marks b What is the value of the resistor R required to replicate the performance of the fuel tank sensor You may assume that the switching transistor has zero resistance when turned on Explain your answer 3 marks See next page ENGINEERING STUDIES 24 SYSTEMS AND CONTROL STAGE 3 Question 25 continued c If you opt to use a standard 56 Q resistor R in your design what is the PWM mark to space ratio for the fuel gauge to read empty Explain your answer Assume the mark condition is a logical one or high output from the microprocessor 3 marks Mark to space ratio Explanation d What is the PWM mark to space ratio for the fuel gauge to read half full Use the same assumptions as in Part c above and also assume that the resistance of the original fuel tank sensor varied linearly with the volume of fuel Show all workings 4 marks See next page SYSTEMS AND CONTROL 25 ENGINEERING STUDIES e STAGE 3 Assuming that the state of charge has been input into the microprocessor and stored as a variable between 0 and 100 create a flow chart that will convert the state of charge value into the required PWM output format 8 marks Hint Assume all mark space pairs add up to 100 divisions For examp
10. is connected in reverse Ws spe Tage ee oe aaa a a ca ae too a 1 l T l l l l l l l l I I l l l I I l I L v V iv Calculate the frequency of Ve Show all workings 2 marks v Calculate the maximum current that can flow through the load Assume the diode is now in the original correct connection Show all workings 2 marks See next page ELECTRONIC ELECTRICAL 75 ENGINEERING STUDIES STAGE 3 c Suppose the switch is closed and the capacitor of 1000 uF now becomes part of the circuit i Explain what primary effect this capacitor has on the load voltage waveform 2 marks ii With reference to the capacitor network shown below calculate the value of capacitor C such that the equivalent overall capacitance is Cr 1000 pF Show all workings 4 marks C C 1000 pF gt l C 600 uF C 600 uF iii What is 1000 pF in nanofarad nF 2 marks See next page ENGINEERING STUDIES 76 ELECTRONIC ELECTRICAL STAGE 3 Question 56 30 marks A circuit is constructed as shown below with five resistors R 2 KQ Ro 2 KQ R3 6 KQ R4 6 KQ and Rs 4 kQ a fuse F and two batteries Vsi 12 V and Vs2 16 V Unless stated otherwise the fuse is behaving like a short circuit with zero resistance zero voltage drop An ideal ammeter is used to obtain readings of s 1 3 75 mA and s2 4 25 mA The diagram below also specifies the
11. of this booklet They can be used for planning your responses and or as additional space if required to continue an answer e Planning If you use the spare pages for planning indicate this clearly at the top of the page e Continuing an answer If you need to use the space to continue an answer indicate in the original answer space where the answer is continued i e give the page number Fill in the number of the question that you are continuing to answer at the top of the page Suggested working time 110 minutes Question 39 25 marks The diagram below shows a rope and pulley system for unloading boxes from a truck and placing them on the ground for unpacking The top pulley block is attached to the end of a beam that is supported at one end on the wall of the factory unit and by a tie rod at the other end See next page MECHANICAL 45 ENGINEERING STUDIES STAGE 3 The operator pulls the rope with a force F and at an angle of 30 to the vertical to lift a box off the back of the truck The truck then moves forward so the operator can lower the box to the ground The beam weighs 100 kg and you can ignore the weight of the tie and the rope pulley system a If the mass of the box is 200 kg show that the force F required to lift it is approximately 490 N Show all workings 2 marks b When the load of 200 kg is being lifted show that the forces caused by the pulley system acting on the end of the beam wh
12. Calculate the energy payback time in years for the solar water heating system Show all workings 3 marks See next page ENGINEERING STUDIES 16 CORE CONTENT STAGE 3 Question 14 15 marks Document 1 Extract from the National Code of Practice for the Installation of Electric Drives in Vehicles in the Document Booklet should be read in conjunction with this question and used as a primary reference when answering the parts of the question a b c d e What are the front and rear impact acceleration limits specified in the standard for the design of battery restraint systems 2 marks Front Rear What is the purpose of battery restraint limits 1 mark A colleague of yours notes that there is no mention in the Code of the reason for the different battery restraint limits Explain why you think that the limits need to be different 2 marks If lithium batteries are used in a vehicle modification does the battery box have to be vented Explain your answer 2 marks Ventilated box Yes No Explanation You are advised that the DC voltage for the main traction battery pack in a modification meets the HAZV classification in the Guidelines What is the minimum possible voltage of the pack to warrant this classification 1 mark See next page CORE CONTENT 17 ENGINEERING STUDIES f STAGE 3 What colour must the wiring cable be to
13. Government of Western Australia School Curriculum and Standards Authority Cw ACE lester Australian Certificate of Education Western Australian Certificate of Education Examination 2012 Question Answer Booklet ENGINEERING STUDIES Please place your student identification label in this box Stage 3 In words Place a tick in one of the Time allowed for this paper following boxes to Reading time before commencing work ten minutes indicate your specialist Working time for paper three hours field Systems and Control Materials required recommended for this paper Mechanical To be provided by the supervisor This Question Answer Booklet Electronic Electrical Multiple choice Answer Sheet Document Booklet Number of additional Data Book answer booklets used if applicable To be provided by the candidate Standard items pens blue black preferred pencils including coloured sharpener correction tape fluid eraser ruler highlighters Special items non programmable calculators approved for use in the WACE examinations measuring and drawing instruments Important note to candidates No other items may be taken into the examination room It is your responsibility to ensure that you do not have any unauthorised notes or other items of a non personal nature in the examination room If you have any unauthorised material with you hand it to the supervisor befo
14. Show all workings 2 marks See next page ENGINEERING STUDIES 70 ELECTRONIC ELECTRICAL STAGE 3 Question 54 continued c Instead of one LED suppose the above dark sensor circuit is now required to drive a cluster of 4 LEDs in a 2 by 2 array The figure below shows such a light module in isolation from the rest of the circuit This module is designed so that each LED operates at a forward voltage of 2 2 V and a current of 16 mA D D R A A V 6V R D D i Determine the required value for resistor R Show all workings 4 marks ii Show that each resistor is dissipating 25 6 mW and each LED is dissipating 35 2 mW of power 2 marks See next page ELECTRONIC ELECTRICAL 71 ENGINEERING STUDIES iii STAGE 3 If the LED D was faulty and behaved like an open circuit how would this affect D Tick the appropriate box below and explain your answer 3 marks The LED D would be the same in brightness brighter dimmer off E Explanation See next page ENGINEERING STUDIES 72 ELECTRONIC ELECTRICAL STAGE 3 Question 55 25 marks Consider the following circuit which has a transformer and a rectifier connected between an AC source and a load Assume the switch is initially open I L gt gt P Oo o 7 8 1 AC Source Transformer Rectifier Load
15. a Suppose an ideal transformer is used Calculate i the secondary voltage Vs of the transformer in the case when the primary voltage Ve 240 VAC Show all workings 2 marks ii the primary current Jp of the transformer in the case when the secondary current Is 0 3 AAC Show all workings 2 marks See next page ELECTRONIC ELECTRICAL 73 ENGINEERING STUDIES b STAGE 3 Suppose the diode used in the rectifier has a forward voltage of 0 6 V the resistor R 100 Q the switch is open and the waveform of the secondary voltage Vs is as shown below Secondary voltage V 42 43 V max ol O I I I I 1 I I I al I I I I I i 4 AE 4 V V 42 43 V min i Sketch the waveform clearly and label its maximum and minimum voltage values for the primary voltage Vp 3 marks Primary voltage V V V ii Sketch the waveform clearly and label its maximum and minimum voltage values for the load voltage V_ Assume no reverse breakdown of the diode 3 marks Load voltage V Vv V See next page ENGINEERING STUDIES 74 ELECTRONIC ELECTRICAL STAGE 3 Question 55 continued iii Sketch the waveform clearly and label its maximum and minimum voltage values for the load voltage V when the diode is connected in reverse by mistake i e when the diode s anode and cathode are swapped around 3 marks Load voltage V when diode
16. a designer to calculate the total cost for the manufacture of a product made from several component parts should include which columns a item number required total cost b number required unit cost c item unit cost number required and total cost d item total cost 5 The safe working load SWL shown in a label on a ladder is intended to indicate the a weight of the ladder b maximum weight of the person using the ladder c number of times the ladder can be used before being given a safety inspection d maximum angle at which the ladder can be placed against a wall 6 Many components used in engineering design have properties that are labelled with a tolerance e g 100 0 1 mm 100 5 Q The value of the tolerance is intended to a allow the property to be varied at will in the manufacturing process b allow for practical small variations in the manufacturing process c indicate to the user that a component may not be fit for purpose d require the designer to review the property before manufacturing commences 7 The selection of the best light bulb for use in your bedside reading lamp should be based primarily on its a power consumption b light output c life expectancy d cost 8 Items of equipment that are used by people are often designed to meet ergonomic requirements Ergonomics concerns a the time taken to perform a task with the equipment b the time it takes the user to become profi
17. ate in the original answer space where the answer is continued i e give the page number Fill in the number of the question s that you are continuing to answer at the top of the page Suggested working time 50 minutes Question 11 15 marks The following flowchart diagram describes the process required to complete the design for a product to be manufactured See next page CORE CONTENT 7 a ENGINEERING STUDIES STAGE 3 Provide a short description of what is commonly taken to be the meaning of each of these steps in the design process 6 marks Design brief Generate alternatives Analyse alternatives Redesign Evaluate alternatives Select solution See next page ENGINEERING STUDIES 8 CORE CONTENT STAGE 3 b c You have been given the task of designing a new battery powered torch flashlight to be used by security guards as they go check on commercial properties during the night List and describe four 4 requirements that could be used for the design of this torch 4 marks One Two Three Four Having produced a number of alternative designs for the torch and analysed each against the nominated performance criteria you are now ready to evaluate the alternatives Describe the process you would recommend for this evaluation so that the best solution is clearly evid
18. ce costs System type Capital cost Yearly operating cost Gas boosted solar water heater 4800 60 Electric water heater 1200 360 i Calculate the extra capital cost of the solar water heater Show all workings 1 mark ii Calculate the annual savings in the operating cost due to the solar water heater Show all workings 1 mark iii Calculate the number of years it will take the solar water heater to pay for itself i e when will the savings equal the extra cost Show all workings 2 marks See next page CORE CONTENT 15 ENGINEERING STUDIES d STAGE 3 Consider the following comparison of the operating energy consumption between a solar system and an electric storage water heater over a period of 15 years Operating energy kWh Solar system Electric system 29 252 118 505 The operating energy is the energy required to heat the water For the solar system this is the energy required for boosting The life cycle energy includes both the capital and operating energy and represents the total energy consumed over the lifetime of the water heating system The capital energy of the solar system is the energy used to manufacture the solar water heater This has been estimated to be 3728 kWh The energy payback time can be calculated as the capital energy divided by the annual energy saving from the solar system compared with the electric system
19. centreline of boat Rudder control arm Hull of boat drive and nut Rudder See next page SYSTEMS AND CONTROL 29 ENGINEERING STUDIES i ii iii iv STAGE 3 The pitch of the thread is 5 mm and the length of the shaft is 100 mm How far will the drive s captive nut move if the shaft is rotated 180 Show all your workings 2 marks If the stepper motor was stepped 20 times to achieve the rotation in i what are the degrees step for the stepper motor 2 marks The torque on the rudder shaft when the boat is travelling at maximum speed and at maximum rate of turn is 1200 x 104 N m If a PM55L 048 Uni Const Ferrite Plastic Magnet MSPL motor is used in the application what is the maximum frequency pulses per second that the stepper motor could be expected to handle The specifications for the motor are in the Document Booklet 1 mark If an alternative motor was used that was torque limited in this application to a maximum frequency of 250 pulses per second and the shaft rotates 10 each step how long would it take it take to move the rudder from being centred to full deflection Assume that the motor is torque limited for the entire period Show all workings 7 marks See next page ENGINEERING STUDIES 30 SYSTEMS AND CONTROL STAGE 3 Question 26 continued d v Describe two 2 possible modifications that could be made to r
20. cient with the use of the equipment c how the use of the equipment may affect the body of the user d the treatment of injuries sustained while using the equipment See next page CORE CONTENT 5 ENGINEERING STUDIES 10 STAGE 3 A time line for a manufacturing task describes a a series of dates by which each stage of the task should be completed b an estimate of the overall time taken to complete the task c the maximum time before starting on the task d an estimate of the expected cost to complete each stage of the task An item of equipment could be described as being recyclable if a it is accepted as waste at the local waste collection depot b it can be sold on to a new owner c all of its components can be reused for some other purpose d all of its components can be reduced to products that can be disposed of in the sewerage system See next page ENGINEERING STUDIES 6 CORE CONTENT STAGE 3 Section One Core content Part B Extended answer 25 45 Marks This section has four 4 questions Answer only three 3 questions Write your answers in the spaces provided Spare pages are included at the end of this booklet They can be used for planning your responses and or as additional space if required to continue an answer e Planning If you use the spare pages for planning indicate this clearly at the top of the page e Continuing an answer If you need to use the space to continue an answer indic
21. des a financial return via reduced hot water energy bills It also reduces the environmental impact of producing energy such as the use of fossil fuel to heat water The owner of the solar water heater only uses and pays for the boosting energy when there is a lack of solar radiation These savings help to pay for the extra cost of the solar water heater over its lifetime The payback time of solar water heating system can be calculated in either economic or energy terms a Suppose the solar water heating system has a collector area of 4 m and the average solar power over a clear and sunny day is 500 joules per second per square metre J s m i Show that the total energy received by the solar collector over the day from sunrise 6 am to sunset 6 pm is 86 4 megajoules MJ 4 marks ii Convert 86 4 MJ to kilowatt hour kWh Show all workings energy J Hint power W time s and 1 J is equal to 1 W s 2 marks See next page ENGINEERING STUDIES 14 CORE CONTENT STAGE 3 b Some electric or gas hot water systems are instantaneous and have no storage They heat the water as it is required Why must solar hot water systems have a hot water storage tank 2 marks c Suppose a gas boosted solar water heater and a corresponding sized electric water heater have the following capital costs and yearly operating costs Assume both systems have the same lifetimes and maintenan
22. direction of the current and the voltage polarity of each circuit element a Use the Kirchhoff s current law to determine the value for the current Jas which is the current that flows from Node A to Node B Show all workings 2 marks See next page ELECTRONIC ELECTRICAL 77 ENGINEERING STUDIES STAGE 3 b Knowing that the power dissipated by the resistor Rs is 36 mW calculate all the resistor currents Provide your answers in the following table Take note of all the current directions as given in the above figure Show all workings 10 marks c Calculate all the resistor voltages Provide your answers in the following table Take note of all the voltage polarity directions as given in the figure Show all workings 10 marks See next page ENGINEERING STUDIES 78 ELECTRONIC ELECTRICAL STAGE 3 Question 56 continued d Calculate the total power supplied by the two batteries Show all workings 2 marks e Suppose the fuse F is blown i Show that the equivalent resistance value as seen by the battery Vsz with the fuse F blown is 5 75 kQ 4 marks ii Calculate the new value for the current when the fuse F is blown Show all workings 2 marks End of Section Two Electronic Electrical End of questions STAGE 3 79 ENGINEERING STUDIES Additional working space
23. e is approximately a 0 06 pF b 0 79 pF c 16 67 pF d 0 013 pF 45 On the schematic symbol of a NPN transistor the arrow points a inward on the base lead b outward on the collector lead c inward on the emitter lead d outward on the emitter lead See next page ENGINEERING STUDIES 60 ELECTRONIC ELECTRICAL STAGE 3 46 47 48 49 50 ol Assuming that the cost of electricity is 20 cents per kWh approximately how long can you operate a 200 W television for 1 a 5 hours b 10 hours c 25 hours d 40 hours An instrument used for measuring potential difference is called a an ammeter b an ohmmeter c a potentiometer d a voltmeter To measure a circuits source voltage the voltmeter must a have the black lead toward the positive side of the source b be placed in series in the circuit c be placed across the source d only be used when the source is switched off In a series resistive circuit the smallest amount of power is dissipated by the a first resistor b last resistor c resistor with the highest resistance d resistor with the lowest resistance A particular capacitor stores 60 uC of charge when 12 V are applied across its plates What is its capacitance value a 0 2uF b Sur c 60 uF d 720 pF If the source voltage of 120 V is applied to the primary of an ideal transformer with a turns ratio of 5 1 what is the voltage across the seco
24. ease remain unchanged Reason 4 marks The current would increase e decrease remain unchanged Reason See next page ENGINEERING STUDIES 66 ELECTRONIC ELECTRICAL STAGE 3 Question 53 continued d The current voltage and resistance values can be measured with appropriate instruments i Draw a circuit diagram below to illustrate clearly how an ammeter should be connected to the circuit in order to measure the current correctly 2 marks ii Draw a circuit diagram below to illustrate clearly how an ohmmeter should be connected to the circuit in order to measure the total resistance R correctly 2 marks See next page ELECTRONIC ELECTRICAL 67 ENGINEERING STUDIES STAGE 3 Question 54 25 marks The figure below shows a basic dark sensor circuit that uses a transistor to switch on the light emitting diode LED when there is a lack of incident light on the light dependent resistor LDR Conversely the LED is deactivated by the transistor when there is sufficient incident light on the LDR Dark sensor circuit a The left part of the above dark sensor circuit is a voltage divider module as shown in the figure below Suppose Vs 6 V R 10 KQ and the resistance of the LDR R2 ranges from 100 Q in very bright light to 200 kQ in darkness Note that an LDR is a resistor whose resistance inc
25. educe the torque load on the motor Indicate clearly the principle involved in each modification and what the impact would be on the performance of the steering system of each modification 6 marks One Two The relative humidity RH in a marine environment can approach 100 Is the PM55L 048 motor suitable for this application Explain your answer 3 marks Suitable Yes No Explanation See next page SYSTEMS AND CONTROL 31 ENGINEERING STUDIES STAGE 3 Question 27 30 marks You are asked to build a system to measure the current drain from the batteries in an electrically powered vehicle The peak current drain is 1000 A DC You are given a current sensor that provides a linear voltage output between 0 V 0A to 5 V 1000 A The output of the sensor is to be directly connected to an ADC Analogue to Digital Converter input of a microprocessor You are given the choice of two different microprocessors to use One device has an 8 bit ADC and the other a 12 bit ADC but costs twice as much The minimum resolution of the 8 bit ADC is 19 mV and the 12 bit ADC is 1 2 mV The required resolution is 0 5 A a Each ADC outputs 0 when the input voltage is 0 V Show that the maximum number output by the ADC associated with the maximum current reading has to be at least 2000 decimal to achieve the specified current resolution 2 marks b Usi
26. end of this booklet They can be used for planning your responses and or as additional space if required to continue an answer e Planning If you use the spare pages for planning indicate this clearly at the top of the page e Continuing an answer If you need to use the space to continue an answer indicate in the original answer space where the answer is continued i e give the page number Fill in the number of the question that you are continuing to answer at the top of the page Suggested working time 110 minutes Question 25 25 marks You are asked to assist with a project to convert a motor vehicle to electric power drive The vehicle is fitted with an analogue fuel gauge that is to be reused as an indicator showing the state of charge of the batteries In the original vehicle this meter was connected to a variable resistance sensor in the fuel tank The resistance of the sensor varied from 0 Q when the tank was empty to 50 Q when it was full The equivalent circuit diagram is Fuel gauge Fuel tank Vehicle 12V contents chassis sensor OV You are asked to develop a microprocessor system that will pulse width modulate a switching transistor to vary the resistance and hence the average current flowing through the fuel gauge The circuit diagram is Fuel gauge Vehicle chassis 12 V OV Switching PWM transistor controller See next page SYSTEMS AND CONTROL 23 ENGINEERING STUDIES STAGE 3 a Describe
27. ent 5 marks See next page CORE CONTENT 9 ENGINEERING STUDIES STAGE 3 Question 12 15 marks The following diagram shows a 3D view of a traffic barrier module of the type often seen near roadworks to control the flow of traffic These traffic barriers are made of a tough impact resistant plastic and can be filled with water 4 400mm DIA 100mm 400mm 800mm Pa 200m The module has a mass of 56 kg when empty There are two 100 mm diameter holes in the top of the barrier module to allow water to be added The water can be emptied from a drain valve not shown in this drawing Ignore the thickness of walls in all calculations See next page ENGINEERING STUDIES 10 CORE CONTENT STAGE 3 a Calculate the total mass of the module when it is filled with water 6 marks b On the next page create a top view of the barrier module Show all dimensions that can be shown on a top view The grid shown is 200 mm by 200 mm 5 marks See next page CORE CONTENT 11 ENGINEERING STUDIES STAGE 3 4 pjiepjppyjiyi i pjij it _ 4 4 4 4 If you wish to ha
28. erature varies with the ambient temperature and the power produced by the engine but usually does not exceed 50 C The water temperature needed for adequate cabin heating is 80 C The temperature of the water can be raised by switching off the radiator solenoid but leaving it off will cause the water to boil The radiator solenoid is to be turned on output Q True whenever the engine is running Input A True and the cabin heater is off Input B False or the cabin heater is on Input B True and the water temperature has exceeded 80 C Input C True i Construct a logic diagram that shows how these signals can be connected to logic gates to achieve the desired result Label each signal input according the conventions above and each logic gate with its type 5 marks Note Use only the logic elements described in the Data Book See next page ENGINEERING STUDIES 38 SYSTEMS AND CONTROL STAGE 3 Question 28 continued ii Construct the truth table for the control of the radiator solenoid 4 marks A B Cc Q In order to reduce the load on the engine cooling system as described in Part c you are also requested to provide an interlock so that the heater solenoid is only able to be turned on by the driver when the ambient air temperature outside the vehicle exceeds 40 C and the heater control has been selected and the engine is running Why is it
29. ere the pulley system is attached are e Vertical force close to 2384 N e Horizontal force close to 245 N Show all workings 8 marks See next page ENGINEERING STUDIES 46 MECHANICAL STAGE 3 Question 39 continued c On the diagram below of the beam draw a schematic representation of the forces resulting from all the applied loads and reactions Point Ais the left hand end of the beam C is the right hand end and B is the mid point of the beam Show each force as an arrow Clearly indicating its direction and label each force with its known value or a blank if its value is currently unknown 5 marks d Show that the force in the tie rod is close to 5748 N 4 marks See next page MECHANICAL 47 ENGINEERING STUDIES STAGE 3 e Calculate the magnitude of the vertical and horizontal components of the reaction force at the left hand end of the beam i e at Point A Show all workings 6 marks See next page ENGINEERING STUDIES 48 MECHANICAL STAGE 3 Question 40 25 marks The diagram below shows a cross section and a partial elevation of a cantilevered balcony The balcony is intended to support the weight of a number of people standing on it The main beams are cantilevered from the wall and spaced at 2 0 m intervals Four cross beams support the decking which is 50 mm thick Decking Cantilever Beam
30. es using just NAND gates by drawing the correctly connected components i NOT gate Use A to describe the input and Q the output and show clearly what any unused inputs are connected to logic 1 or 0 to produce the desired result 2 marks ii OR gate Both A and Not A and B and Not B are available to be used as inputs as you see fit and Q is to be used to describe the output Show clearly what any unused inputs are connected to logic 1 or 0 to produce the desired result 2 marks See next page ENGINEERING STUDIES 36 SYSTEMS AND CONTROL STAGE 3 Question 28 continued b Complete the truth table for the following circuit What logic building block does it perform 3 marks A Q B Input A Input B Output Q Logic block function c You are asked to design a control system that will use the heat from an engine water cooling jacket to provide cabin heating in a vehicle when the driver turns on the heater A diagram of the proposed system is as follows Engine Engine radiator heater Radiator in cabin Radiator Engine heat Tem emperature solenoid valve exchanger and oheari water pump See next page SYSTEMS AND CONTROL 37 ENGINEERING STUDIES STAGE 3 The heat from the cooling jacket water is dissipated through a radiator mounted in the front of the vehicle when the cabin heater is not in use and the cooling water temp
31. le half charge is 50 50 See next page ENGINEERING STUDIES 26 SYSTEMS AND CONTROL STAGE 3 Question 25 continued f Describe an alternative hardware solution using a servo motor and any other components you feel are necessary that could be used in place of the PWM solution 2 marks g Would you use your alternative solution in preference to the PWM solution Explain your answer 2 marks Use alternative solution Yes No Explanation See next page SYSTEMS AND CONTROL 27 ENGINEERING STUDIES STAGE 3 Question 26 25 marks Document 2 in the Document Booklet The NMB MAT Stepper Motor should be read in conjunction with this question when answering the parts of the question a List three 3 advantages that a belt drive has over a chain drive 3 marks One Two Three b Describe one 1 advantage that a chain drive has over a belt drive 1 mark See next page ENGINEERING STUDIES 28 SYSTEMS AND CONTROL STAGE 3 Question 26 continued c Aworm gear driven by a stepper motor is used in a steering control system for a model boat The captive nut is directly connected to the steering arm of the rudder Plan view of rudder and worm gear control system Rudder Rudder Rudder axle bearing Worm Rudder control r arm tiller g Rudder bearing Side view cross section through
32. ndary load a 24V b 60V c 120V d 600V See next page ELECTRONIC ELECTRICAL 61 ENGINEERING STUDIES STAGE 3 52 A transistor has a collector current Jc of 10 mA How much is the base current Js if the transistor has a B of 200 a 50 pA b 20 mA c 0 5A d 2A See next page ENGINEERING STUDIES 62 ELECTRONIC ELECTRICAL STAGE 3 Part B Extended answer 55 105 Marks This part has four 4 questions Answer all questions Write your answers in the spaces provided Spare pages are included at the end of this booklet They can be used for planning your responses and or as additional space if required to continue an answer e Planning If you use the spare pages for planning indicate this clearly at the top of the page e Continuing an answer If you need to use the space to continue an answer indicate in the original answer space where the answer is continued i e give the page number Fill in the number of the question that you are continuing to answer at the top of the page Suggested working time 110 minutes Question 53 25 marks A DC voltage source of unknown voltage value V is applied across a resistor network as shown in the circuit diagram below where R 1 KQ R 2 KQ R 1 KQ and R 1 KQ a Determine the value of the total resistance R which is the equivalent resistance value seen by the voltage source Show all workings 3 marks See next page
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34. ng the maximum output number in Part a show that the resolution required from the ADC is approximately 2 5 mV Show all workings 3 marks See next page ENGINEERING STUDIES 32 SYSTEMS AND CONTROL STAGE 3 Question 27 continued c On the basis of your answer to Part b which microprocessor would you use to achieve the resolution required Explain your answer 2 marks Chosen microprocessor Explanation d A system is to be fitted with a microprocessor based controller that monitors the power being used and shuts it down if pre set limits are exceeded The following design requirements have been specified for the monitor The microprocessor is required to drive an LCD display via its serial port a LED over current warning indicator and a relay that is used to turn the system on The relay is to be turned on once the microprocessor has been initialised The current is to be sensed once a second and the LCD updated with the new value Should the current reading exceed 1000 A the LED is to be turned ON Should the current exceed 1200 A for more than a minute the relay is to be turned off i Construct a flow chart that incorporates these requirements 9 marks See next page SYSTEMS AND CONTROL 33 ENGINEERING STUDIES d ii iii STAGE 3 Will the monitor cause the system to fail safely under all conditions if the power supply circuit to the microproce
35. not necessary to include the engine running as one of the inputs to the logic circuit when the heater is operated Explain your answer Why it is not necessary Explanation 3 marks See next page SYSTEMS AND CONTROL 39 ENGINEERING STUDIES e STAGE 3 When the control system for the radiator solenoid is built and tested it is noted that the solenoid valve is switching on and off every couple of seconds when the cabin heater is turned on This could cause premature failure of the solenoid i Explain why this is happening 2 marks ii Describe a possible solution to the problem and explain briefly how it would work 2 marks Solution How it works iii Would you use a programmable controller or retain a hardwired design approach Circle your choice and explain your answer 2 marks Programmable controller Hardwired design Explanation End of Section Two Systems and Control See next page ENGINEERING STUDIES 40 STAGE 3 This page has been left blank intentionally See next page MECHANICAL 41 ENGINEERING STUDIES STAGE 3 Section Two Specialist field Mechanical 65 115 Marks This section has two 2 parts PartA Multiple choice Answer all questions Part B Extended answer Answer all questions Suggested working time 120 minutes Part A Multiple choice 10 10 Marks This part has ten 10 questions Answer all que
36. on external stairways Boxes for desktop computers Piping in desalination plants End of Section Two Mechanical See next page ENGINEERING STUDIES 58 STAGE 3 This page has been left blank intentionally See next page ELECTRONIC ELECTRICAL 59 ENGINEERING STUDIES STAGE 3 Section Two Specialist field Electronic Electrical 65 115 Marks This section has two 2 parts PartA Multiple choice Answer all questions PartB Extended answer Answer all questions Suggested working time 120 minutes Part A Multiple choice 10 10 Marks This part has ten 10 questions Answer all questions on the separate Multiple choice Answer Sheet provided For each question shade the box to indicate your answer Use only a blue or black pen to shade the boxes If you make a mistake place a cross through that square then shade your new answer Do not erase or use correction fluid tape Marks will not be deducted for incorrect answers No marks will be given if more than one answer is completed for any question Suggested working time 10 minutes 43 When an additional resistor is connected across an existing parallel resistive circuit the total resistance a decreases b increases c remains the same d is impossible to determine without knowing the actual resistance values 44 If0 47 uF 0 22 uF and 0 1 uF capacitors are connected in series the overall capacitance valu
37. on layer must be Most normal ironwork corrodes because it develops a It was known as early as 1821 that iron chromium alloys were corrosion resistant but they were not useful because See next page ENGINEERING STUDIES 56 MECHANICAL STAGE 3 Question 42 continued e f h i In harsh environments what percentage of chromium is recommended for stainless steel 1 mark Chromium forms a passivation layer on the surface of stainless steel What is this layer composed of and how does it provide protection if the surface is scratched 2 marks Layer is Protection Name five 5 common applications for stainless steel 5 marks One Two Three Four Five Name one notable Australian application of stainless steel and how much was required to build it 2 marks Describe the steps in the process that is used to prepare stainless steel before it is ready for sale 5 marks One Two Three Four Five See next page MECHANICAL 57 ENGINEERING STUDIES STAGE 3 j For the following manufactured components indicate whether you would recommend that they be made from stainless steel and give short justifications for your answers You need to consider that stainless steel is likely to be much more expensive to use than normal grades of steel 6 marks Component S stainless steel Component Reason yes no Handrails
38. ooth the input signal Capacitors are typically connected between control system inputs and ground to a remove unwanted high frequency noise voltages b limit the voltage on the input pins c rectify the incoming signal d disable unused inputs A Proportional Control System would be used in which of the following applications in a typical house i turning on a fan ii adjusting the temperature of an air conditioner iii setting the timer in a microwave oven iv dimming a light i ii iv b ii and iv ii iii and iv ii See next page SYSTEMS AND CONTROL 21 ENGINEERING STUDIES 23 24 STAGE 3 The accuracy of the output from an ADC is primarily determined by the a number of bits used in the conversion b supply voltage c magnitude and frequency of the input signal d output load In a Pulse Width Modulation System which of the following vary with changes to the input signal i the amplitude of the output pulses ii the frequency of the output pulses iii the width of the output pulses iv the energy of the output pulses a i ii iii and iv b only iii and iv c only iii d only iv See next page ENGINEERING STUDIES 22 SYSTEMS AND CONTROL STAGE 3 Part B Extended answer 55 105 Marks This part has four 4 questions Answer all questions Write your answers in the spaces provided Spare pages are included at the
39. re reading any further Copyright School Curriculum and Standards Authority 2012 Ref 12 047 ENGINEERING STUDIES 2 STAGE 3 Structure of this paper Number of Number of Suggested Mark questions questions to working time si Percentage Section available be answered minutes Vallable of exam Section One Core content Part A Multiple choice 10 10 10 10 10 Part B Extended answer 4 3 50 45 25 Section Two Systems and Control Part A Multiple choice 10 10 10 10 10 Part B Extended answer 4 4 110 105 55 Section Two Mechanical Part A Multiple choice 10 10 10 10 10 Part B Extended answer 4 4 110 105 55 Section Two Electronic Electrical Part A Multiple choice 10 10 10 10 10 Part B Extended answer 4 4 110 105 55 Total 100 Instructions to candidates Ns The rules for the conduct of Western Australian external examinations are detailed in the Year 12 Information Handbook 2012 Sitting this examination implies that you agree to abide by these rules 2 Answer the questions according to the following instructions Sections One and Two Part A Answer all questions on the separate Multiple choice Answer Sheet provided For each question shade the box to indicate your answer Use only a blue or black pen to shade the boxes If you make a mistake place a cross through that square then shade your new answer Do not erase or use correction fluid tape Marks will not be
40. reases with decreasing intensity of incident light Therefore in the voltage divider module the output voltage Vo varies as R changes See next page ENGINEERING STUDIES 68 ELECTRONIC ELECTRICAL STAGE 3 Question 54 continued a i By using the voltage division principle write a mathematical expression for V in terms of R4 Ro and Vs 2 marks ii Show that V swings from 59 4 mV to 5 71 V 2 marks iii Calculate the value for R such that V 0 7 V Show all workings 2 marks iv Suppose a 4 band colour coded resistor of 10 KQ with 5 tolerance is used to implement R What colours would this resistor display State the colours for each of the bands 4 marks Band one Band two Band three Band four See next page ELECTRONIC ELECTRICAL 69 ENGINEERING STUDIES STAGE 3 b Suppose the above dark sensor circuit has the following parameters Parameters Source voltage Vs 6V Resistor R 220 Q LED on voltage Viep on 2V Transistor on voltage Vse on 0 7 V Transistor saturation voltage Vce sat OV Transistor current gain B 100 Determine the amount of current that flows through the LED when i the resistance value of the LDR reaches a high enough value to turn on and operate the transistor at its saturation region Show all workings 4 marks ii the transistor is operating in the cut off region
41. s This part has ten 10 questions Answer all questions on the separate Multiple choice Answer Sheet provided For each question shade the box to indicate your answer Use only a blue or black pen to shade the boxes If you make a mistake place a cross through that square then shade your new an swer Do not erase or use correction fluid tape Marks will not be deducted for incorrect answers No marks will be given if more than one answer is completed for any question Suggested working time 10 minutes Te An engineering drawing of an object would normally have a scale value shown on the drawing in the form for example Scale 1 10 This can be interpreted as the a drawing is 10 times larger than the real object b drawing is 10 times smaller than the real object c dimensions shown on the drawing should be multiplied by 10 when manufacturing the object d dimensions shown on the drawing should be divided by 10 when manufacturing the object 2 The most important aspect of a design solution is its a safety b cost c function d marketability 3 The main purpose of a 3D drawing of an object is to a show the true shape of the object b provide a drawing suitable for a machinist to manufacture c provide a good impression of the overall shape of the object d enable dimensions to be added to the drawing See next page ENGINEERING STUDIES 4 CORE CONTENT STAGE 3 4 A chart used to assist
42. s to a stop Show that the ram will contract about 0 55 m before the wagon comes to a stop 6 marks d Show that the average de acceleration imposed on the wagon is about 27 8 m s while it is coming to rest 4 marks e Calculate the time taken for the wagon to come to rest after it first contacts the buffer ram 4 marks See next page ENGINEERING STUDIES 54 MECHANICAL STAGE 3 Question 41 continued f Explain where all the kinetic energy has gone once the wagon has come to rest 3 marks See next page MECHANICAL 55 ENGINEERING STUDIES STAGE 3 Question 42 30 marks This question should be answered with reference to Document 3 Stainless Steel in the Document Booklet Stainless steel is a particular type of steel Answer the following questions relating to the properties and uses of stainless steel a b c d Describe two 2 properties of stainless steel that make it suitable for use in external environments 2 marks One Two Stainless steel is an alloy of steel with which additional element What is the approximate percentage of that element by mass 2 marks Element Percentage by mass When was it reported in the press that stainless steel was invented and for what use 2 marks When Use Complete the following sentences 3 marks To be protective the corrosi
43. ssor fails Assume that the system is safe when it is powered down Explain your answer 2 marks Yes No Explanation Will the monitor cause the system to fail safely under all conditions when the power supply to the microprocessor device is normal Identify two 2 fault conditions that support your answer and explain what happens in each of these conditions Assume that the system is safe when it is powered down 5 marks Yes No Fault condition one Explanation Fault condition two Explanation See next page ENGINEERING STUDIES 34 SYSTEMS AND CONTROL STAGE 3 Question 27 continued e How you would interface the relay to the microprocessor Include a circuit diagram in your answer showing each of the components involved Describe the purpose of all components except the microprocessor and relays 5 marks The over current warning LED is connected to the microprocessor output pin via a dropping resistor The voltage on the output pin is 4 5 V in the high LED On state The voltage drop across the LED when it is conducting is 1 2 V Calculate the value of the dropping resistor such that the current flowing into the microprocessor is limited to 10 mA Show all workings 2 marks See next page SYSTEMS AND CONTROL 35 ENGINEERING STUDIES STAGE 3 Question 28 25 marks a Show how to construct the following gat
44. stions on the separate Multiple choice Answer Sheet provided For each question shade the box to indicate your answer Use only a blue or black pen to shade the boxes If you make a mistake place a cross through that square then shade your new answer Do not erase or use correction fluid tape Marks will not be deducted for incorrect answers No marks will be given if more than one answer is completed for any question Suggested working time 10 minutes 29 A pin jointed truss carries its applied loading by a combination of a bending moments b shear forces c axial forces d gravity forces 30 Ifan object is moving in a straight line at constant velocity it can be described as being in a state of a acceleration b equilibrium c instability d zero gravity 31 Compared with structural steel copper can be described as being a stiffer b less dense c stronger d more ductile 32 Ina tensile test of a steel specimen the amount of energy absorbed by the specimen during the test is found from the a area under the load extension graph b area under the stress strain graph c total force multiplied by the total extension d maximum stress divided by the maximum strain See next page ENGINEERING STUDIES 42 MECHANICAL STAGE 3 33 34 35 36 37 A uniformly distributed load placed on a beam is best described as a force that a is applied at regular intervals along the beam
45. t page SYSTEMS AND CONTROL 19 ENGINEERING STUDIES STAGE 3 Section Two Specialist field Systems and Control 65 115 Marks This section has two 2 parts PartA Multiple choice Answer all questions Part B Extended answer Answer all questions Suggested working time 120 minutes Part A Multiple choice 10 10 Marks This part has ten 10 questions Answer all questions on the separate Multiple choice Answer Sheet provided For each question shade the box to indicate your answer Use only a blue or black pen to shade the boxes If you make a mistake place a cross through that square then shade your new an swer Do not erase or use correction fluid tape Marks will not be deducted for incorrect answers No marks will be given if more than one answer is completed for any question Suggested working time 10 minutes 15 16 ie A logic gate with inputs A and B and output 4 8 is commonly called a a XOR gate b NOR gate c NAND gate d NOT gate If a typical microprocessor controller is required to drive a 50 mA load from one of its output pins then it is a only possible if none of the other outputs on the device are in use b always possible regardless of the number of other outputs in use c not possible to source or sink such a load current d only possible if the microprocessor supply voltage is doubled If the power supply to a microprocessor is switched off then back on and it has not
46. ve a second attempt at this item the grid is repeated at the end of the Question Answer Booklet Indicate clearly on this page if you have used the second grid and cancel the working on the drawing on this page See next page ENGINEERING STUDIES 12 CORE CONTENT STAGE 3 c Provide an explanation as to why it is useful to have a barrier module that can be filled with water 2 marks d The water is added to the barrier module from a water tanker truck that has a 100 mm diameter hose that just fits into one of the holes in the top of the module Explain why a second hole in the top is necessary 2 marks See next page CORE CONTENT 13 ENGINEERING STUDIES STAGE 3 Question 13 15 marks Solar water heaters have been developed manufactured and used in Australia since the 1950s They are recognised as a key part of a sustainable home A solar water heating system has four basic parts 1 a collector to absorb thermal energy from sunlight 2 a storage tank to store the collected heat energy in water 3 a circulation system to transfer collected energy from the collector to the tank 4 a booster heater either electric or gas to further heat the water if solar radiation is inadequate to ensure sufficient hot water is available on demand There are economic and environmental benefits of using a solar water heater By utilising free energy from the Sun the solar water heating system provi
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