Download engineering studies - School Curriculum and Standards Authority

Western Australian Certificate of Education
Examination, 2012
Question/Answer Booklet
ENGINEERING
STUDIES
Please place your student identification label in this box
Stage 3
Student Number:
In figures
In words
Time allowed for this paper
Reading time before commencing work:
Working time for paper:
ten minutes
three hours
Place a tick in one of the
following boxes to
indicate your specialist
field.
Systems and Control
Materials required/recommended for this paper
To be provided by the supervisor
This Question/Answer Booklet
Multiple-choice Answer Sheet
Document Booklet
Data Book
To be provided by the candidate
Mechanical
Electronic/Electrical
Number of additional
answer booklets used
(if applicable):
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
before reading any further.
Copyright © School Curriculum and Standards Authority 2012
Ref: 12-047
ENGINEERING STUDIES
2
STAGE 3
Structure of this paper
Section
Suggested
Number of Number of
questions questions to working time
available be answered (minutes)
Marks
available
Percentage
of exam
Section One:
Core content
Part A: Multiple-choice
Part B: Extended answer
10
4
10
3
10
50
10
45
10
25
Section Two:
Systems and Control
Part A: Multiple-choice
Part B: Extended answer
10
4
10
4
10
110
10
105
10
55
Section Two:
Mechanical
Part A: Multiple-choice
Part B: Extended answer
10
4
10
4
10
110
10
105
10
55
Section Two:
Electronic/Electrical
Part A: Multiple-choice
Part B: Extended answer
10
4
10
4
10
110
10
105
10
55
Total
100
Instructions to candidates
1.
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 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.
● Planning: If you use the spare pages for planning, indicate this clearly at the top of the
page.
● 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.
Part A:
Multiple-choice Answer all questions
Part B:
Extended answer
Answer three (3) questions
Suggested working time: 60 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.
1.
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)
(b)
(c)
(d)
drawing is 10 times larger than the real object.
drawing is 10 times smaller than the real object.
dimensions shown on the drawing should be multiplied by 10 when
manufacturing the object.
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)
(b)
(c)
(d)
show the true shape of the object.
provide a drawing suitable for a machinist to manufacture.
provide a good impression of the overall shape of the object.
enable dimensions to be added to the drawing.
See next page
ENGINEERING STUDIES
STAGE 3
4
CORE CONTENT
4.
A chart used to assist a designer to calculate the total cost for the manufacture of a
product made from several component parts should include which columns?
(a)
(b)
(c)
(d)
item, number required, total cost
number required, unit cost
item, unit cost, number required and total cost
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.
7.
8.
Many components used in engineering design have properties that are labelled with
a tolerance, e.g. 100 ± 0.1 mm, 100 ± 5 Ω. The value of the tolerance is intended to
(a)
(b)
(c)
(d)
allow the property to be varied at will in the manufacturing process.
allow for practical small variations in the manufacturing process.
indicate to the user that a component may not be fit for purpose.
require the designer to review the property before manufacturing commences.
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.
Items of equipment that are used by people are often designed to meet ergonomic
requirements. Ergonomics concerns
(a)
(b)
(c)
(d)
the time taken to perform a task with the equipment.
the time it takes the user to become proficient with the use of the equipment.
how the use of the equipment may affect the body of the user.
the treatment of injuries sustained while using the equipment.
See next page
CORE CONTENT
9.
5
ENGINEERING STUDIES
STAGE 3
A time line for a manufacturing task describes
(a)
(b)
(c)
(d)
a series of dates by which each stage of the task should be completed.
an estimate of the overall time taken to complete the task.
the maximum time before starting on the task.
an estimate of the expected cost to complete each stage of the task.
10. 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
STAGE 3
6
CORE CONTENT
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.
• Planning: If you use the spare pages for planning, indicate this clearly at the top of the page.
• 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.
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
ENGINEERING STUDIES
STAGE 3
(a) 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
STAGE 3
(b)
8
CORE CONTENT
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:
(c)
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 evident.
(5 marks)
See next page
CORE CONTENT
CORE CONTENT
9
9
Question 12
ENGINEERING STUDIES
STAGE 3
ENGINEERING STUDIES
STAGE 3
(15 marks)
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.
The following
diagram
shows
a perspective view of a traffic barrier module, of the type often
seen near road works to control the flow of traffic. These traffic barriers are made of a tough
impact-resistant plastic and can be filled with water.
The module weighs 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
The
module
hasdrawing).
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
See next page
ENGINEERING STUDIES
STAGE 3
10
CORE CONTENT
(a) Calculate the total mass of the module when it is filled with water.
(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
(6 marks)
CORE CONTENT
11
ENGINEERING STUDIES
STAGE 3
If you wish to have 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
STAGE 3
12
CORE CONTENT
(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 provides 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 m2 and the average
solar power over a clear and sunny day is 500 joules per second per square metre
(J s-1 m2).
(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)
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.
(ii)
See next page
(2 marks)
ENGINEERING STUDIES
STAGE 3
14
CORE CONTENT
(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 maintenance 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
(d)
15
ENGINEERING STUDIES
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.
Calculate the energy payback time in years for the solar water heating system. Show all workings.
(3 marks)
See next page
ENGINEERING STUDIES
STAGE 3
16
CORE CONTENT
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)
What are the front and rear impact acceleration limits specified in the standard for the
design of battery restraint systems? (2 marks)
Front:
Rear:
(b)
What is the purpose of battery restraint limits?
(1 mark)
(c)
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)
(d)
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:
(e)
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
(f)
17
ENGINEERING STUDIES
STAGE 3
What colour must the wiring cable be to comply with the Guidelines? (1 mark)
(g)
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:
(h)
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
18
STAGE 3
Section Two: Specialist fields
65% (115 Marks)
Candidates are required to choose one of the following options, according to which specialist
field they studied in 2012.
Tick one of the boxes below to indicate your choice of option.
Question numbers
Pages
Systems and Control
15−28
19−39
Mechanical
29−42
41−57
Electronic/Electrical
43−56
59−78
Specialist field
Now turn to the relevant pages and answer the questions for the specialist field you have
selected.
See next 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.
Answer all questions
Part A:
Multiple-choice 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 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.
15.
A logic gate with inputs A and B and output A+B is commonly called a
(a)
(b)
(c)
(d)
16.
If a typical microprocessor controller is required to drive a 50 mA load from one of its
output pins, then it is
(a)
(b)
(c)
(d)
17.
If the power supply to a microprocessor is switched off then back on, and it has not
been programmed to cater for a power interruption, then the
(a)
(b)
(c)
(d)
XOR gate.
NOR gate.
NAND gate.
NOT gate.
only possible if none of the other outputs on the device are in use.
always possible regardless of the number of other outputs in use.
not possible to source or sink such a load current.
only possible if the microprocessor supply voltage is doubled.
program resumes at the last instruction being executed before the power
was switched off.
processor restarts the program at the first instruction.
microprocessor must be reprogrammed because its ROM has been erased.
result is unpredictable.
See next page
ENGINEERING STUDIES
STAGE 3
20
SYSTEMS AND CONTROL
18.
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)
(b)
(c)
(d)
19.
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)
(b)
(c)
(d)
20.
If an AC voltage is applied to a diode, the diode will block
2.4 cm
12 cm
24 cm
60 cm
only when the driver is considered to be part of the control loop.
only when the driver is not part of the control loop.
irrespective of whether the driver is part of the loop.
only when the vehicle is in motion.
(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 smooth the input signal.
21.
Capacitors are typically connected between control system inputs and ground to
(a)
(b)
(c)
(d)
22.
A Proportional Control System would be used in which of the following applications in a
typical house?
remove unwanted high frequency ‘noise’ voltages.
limit the voltage on the input pins.
rectify the incoming signal.
disable unused inputs.
(i)
(ii)
(iii)
(iv)
turning on a fan
adjusting the temperature of an air conditioner
setting the timer in a microwave oven
dimming a light
(a)
(i), (ii), (iv)
(b)
(ii) and (iv)
(c)
(ii), (iii) and (iv)
(d)
(ii)
See next page
SYSTEMS AND CONTROL
21
ENGINEERING STUDIES
STAGE 3
23.
The accuracy of the output from an ADC is primarily determined by the
(a)
(b)
(c)
(d)
number of bits used in the conversion.
supply voltage.
magnitude and frequency of the input signal.
output load.
24. In a Pulse Width Modulation System, which of the following vary with changes to the input
signal?
(i)
(ii)
(iii)
(iv)
the amplitude of the output pulses
the frequency of the output pulses
the width of the output pulses
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
Part B: Extended
answer
55%CONTROL
(105 marks)
ENGINEERING
STUDIES
24
SYSTEMS AND
STAGE 3
This section has four (4) questions. Answer all questions. Write your answers in the spaces
ENGINEERING STUDIES
22
SYSTEMS AND CONTROL
provided.
Part
B: Extended answer
55% (105 marks)
STAGE 3
Spare
pages
included
at the endAnswer
of this booklet.
They can
beyour
used
for (105
planning
This
section
hasare
four
(4) questions.
all questions.
Write
answers
in
theyour
spaces
Part B: Extended
answer
55%
Marks)
responses and/or as additional space if required to continue an answer.
provided.
• four
Planning:
If you useAnswer
the spare
pages for planning,
indicate
thisinclearly
at the top of the page.
This part has
(4) questions.
all questions.
Write your
answers
the spaces
Spare
pages
are
included
at
the
end
of
this
booklet.
They
can
be
used
for
planning
your
provided. • Continuing an answer: If you need to use the space to continue an answer, indicate in the
responses
and/or
as
additional
space
if
required
to
continue
an
answer.
original answer space where the answer is continued, i.e. give the page number. Fill in the
• Planning:
the spare
pages
for planning,
this at
clearly
at of
thethe
toppage.
of the page.
number Ifofyou
the use
question(s)
that
you are
continuingindicate
to answer
the top
Spare pages are included at the end of this booklet. They can be used for planning your
• Continuing an answer: If you need to use the space to continue an answer, indicate in the
responses and/or as additional space if required to continue an answer.
Suggested
working
time:where
110 the
minutes.
original answer
space
answer is continued, i.e. give the page number. Fill in the
● Planning: If you use the spare pages for planning, indicate this clearly at the top of the page.
number of the question(s) that you are continuing to answer at the top of the page.
● Continuing an answer: If you need to use the space to continue an answer, indicate in the
original
answer space
answer
is continued, i.e. give the page number. Fill in the (25 marks)
Suggested
working
time:the
110
minutes.
Question
25 where
number of the question that you are continuing to answer at the top of the page.
Suggested
working
time: 110
minutes.
You
are 25
asked
to assist
with a project to convert a motor vehicle to electric power drive.
The
Question
(25 marks)
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
sensortovaried
from
0 ohms
are asked
to assist
with
a project
to convert
a motor
vehicle
electric
power
drive.when
Thethe
QuestionYou
25
(25
marks)
tank was
empty
50analogue
ohms when
was full.
vehicle
is fitted
withtoan
fuelit gauge
thatThe
is toequivalent
be reusedcircuit
as andiagram
indicatorisshowing the
state of
of the
batteries.
In the original
thiselectric
meter power
was connected
You are asked
tocharge
assist with
a project
to convert
a motorvehicle,
vehicle to
drive. Theto a variable
resistance
sensor
in
the
fuel
tank.
The
resistance
of
the
sensor
varied
from
0 ohms
vehicle is fitted with an analogue fuel gauge that is to be reused as an indicator showing
the when the
tank was
empty
to 50 ohms
it was
full. The
equivalent
circuit diagram
is
state of charge
of the
batteries.
In thewhen
original
vehicle,
this meter
was connected
to a variable
resistance sensor in the fuel tank. The resistance of the sensor varied from 0 Ω when the tank
Gauge
was empty to 50 Ω when it Fuel
was full.
The equivalent circuit diagram is
12 V
Fuel
gauge
Fuel
Gauge
12 V
Fuel Tank
Contents
Sensor
Fuel
tank
Fuel
Tank
contents
Contents
sensor
Sensor
Vehicle
Chassis
(0V)
Vehicle
Vehicle
chassis
Chassis
(0V)
(0V)
You are asked to develop a microprocessor system that will pulse width modulate a switching
transistor
to vary
the resistance and
hence
thewill
average
current
flowing athrough
the fuel gauge.
You are asked
to develop
a microprocessor
system
that
pulse width
modulate
switching
The
circuit
diagram
is:
transistor to vary the resistance and hence the average current flowing through the fuel gauge. You
are asked
The circuit
diagram
is 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 diagramFuel
is: Gauge
Fuel gauge
Vehicle
Vehicle
R
chassis
Fuel Gauge
Chassis
12 V
(0V)
(0V)
Vehicle
R
Chassis
12 V
(0V)
Switching
Switching
PWM
PWM
transistor
Transistor
Controller
controller
PWM
Controller
Switching
Transistor
See next page
See next page
See next page
SYSTEMS AND CONTROL
23
ENGINEERING STUDIES
STAGE 3
(a)
Describe 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
STAGE 3
24
SYSTEMS AND CONTROL
Question 25 (continued)
(c)
If you opt to use a standard 56 Ω 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
STAGE 3
(e)
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 example, half charge is
50:50.
See next page
ENGINEERING STUDIES
STAGE 3
26
SYSTEMS AND CONTROL
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. See next page
(1 mark)
ENGINEERING STUDIES
STAGE 3
28
SYSTEMS AND CONTROL
Question 26 (continued)
ENGINEERING STUDIES
30
SYSTEMS AND CONTROL
STAGE
3
(c)
A worm 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.
(c)
A worm 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
Plan worm
View ofgear
Rudder
and
and Worm Gear
control system
Rudder
Rudder
Rudder
axle
Axle
Control System
Worm
Worm
gear
Gear
Rudder
Rudder
bearing
Bearing
Rudder control
arm (tiller)
Rudder
Rudder
bearing
bearing
Stepper
Stepper
motor
Motor
Captive
nut
Side view
Side
View section
Cross section
cross
through
through
centrelineof
of boat
boat
centreline
Rudder
control arm
Worm
drive
and nut
Hullof
of
Hull
Boat
boat
Rudder
bearing
Rudder
axle
See next page
Rudder
SYSTEMS AND CONTROL
29
ENGINEERING STUDIES
STAGE 3
(i)
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)
(ii)
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)
(iii)
The torque on the rudder shaft when the boat is travelling at maximum speed and at maximum rate of turn is 1200 × 10-4 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)
(iv)
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
STAGE 3
30
SYSTEMS AND CONTROL
Question 26 (continued)
(v)Describe two (2) possible modifications that could be made to reduce 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:
(d)
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
Question 27 ENGINEERING STUDIES
STAGE 3
(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 (0 A) 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)
Using 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
STAGE 3
32
SYSTEMS AND CONTROL
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. See next page
(9 marks)
SYSTEMS AND CONTROL
(d)
(ii)
33
ENGINEERING STUDIES
STAGE 3
Will the monitor cause the system to fail safely under all conditions if the power
supply circuit to the microprocessor fails? Assume that the system is safe when
it is powered down. Explain your answer.
(2 marks)
Yes/No:
Explanation:
(iii) 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
STAGE 3
34
SYSTEMS AND CONTROL
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)
(f) 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
Question 28 (a)
ENGINEERING STUDIES
STAGE 3
(25 marks)
Show how to construct the following gates 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
SYSTEMS AND CONTROL
39
SYSTEMS AND CONTROL
39
ENGINEERING STUDIES
STAGE 3
ENGINEERING
STUDIES
STAGE 3
ENGINEERING STUDIES
36
SYSTEMS AND CONTROL
STAGE
(b) 3 Complete the truth table for the following circuit. What logic building block does it
perform?
(b)
Complete the truth table for the following circuit. What logic building block does it
Question 28 (continued)
perform?
(3 marks)
(b)
Complete the truth table for the following circuit. What logic building block does it
(3 marks)
perform? (3 marks)
Input A
Input B
Input A
Input A
Output Q
Input B
Input B
Output Q
Output Q
Logic
Block
Function:_________________________________________________
Logic
block
function:
Logic Block Function:_________________________________________________
are asked
to design
a control
system
will use
the heat
an engine
water
(c) (c) YouYou
are asked
to design
a control
system
that that
will use
the heat
fromfrom
an engine
water
cooling
jacket
to
provide
cabin
heating
in
a
vehicle
when
the
driver
turns
on
the
cooling jacket
cabin
heating
in a a
vehicle
the that
driver
heater.
(c) to provide
You are
asked
to design
controlwhen
system
willturns
use on
thethe
heat
from an engine water
heater.of Athe
diagram
of
the
proposed
system
is
as
follows:
A diagram
proposed
system
is
as
follows.
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:
Cabin
Cabin
heater
Heater
on/off
On/Off
Engine
Engine
radiator
Radiator
Cabin
Heater
On/Off
Engine
Engine
Radiator
Engine
Cabin
Cabin
heater
Heater
T
Cabin
Heater
T
Radiator
Radiatorin
incabin
Cabin
Radiator
Radiator
solenoid
Solenoidvalve
Valve
EngineHeat
heat
Engine
Temperature
Temperature
exchanger
Exchanger and
and
Radiator
sensor
EngineSensor
Heat
Water
Pump
water
pump
Solenoid
Valve
Exchanger and
Water Pump
See next page
See next page
See next page
Temperature
Sensor
Radiator
in Cabin
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 temperature
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
STAGE 3
38
SYSTEMS AND CONTROL
Question 28 (continued)
(ii)
Construct the truth table for the control of the radiator solenoid. A
B
C
(4 marks)
Q
(d)
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 not necessary to include the engine running as one of the inputs to the logic
circuit when the heater is operated? Explain your answer. (3 marks)
Why it is not necessary:
Explanation:
See next page
SYSTEMS AND CONTROL
39
ENGINEERING STUDIES
STAGE 3
(e)
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
This page has been left blank intentionally
See next page
STAGE 3
MECHANICAL
41
ENGINEERING STUDIES
STAGE 3
Section Two: Specialist field—Mechanical
65% (115 Marks)
This section has two (2) parts.
Part A:
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
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)
(b)
(c)
(d)
30.
If an 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.
In a tensile test of a steel specimen, the amount of energy absorbed by the specimen
during the test is found from the
(a)
(b)
(c)
(d)
bending moments.
shear forces.
axial forces.
gravity forces.
area under the load-extension graph.
area under the stress-strain graph.
total force multiplied by the total extension.
maximum stress divided by the maximum strain.
See next page
ENGINEERING STUDIES
STAGE 3
42
MECHANICAL
33.
A uniformly distributed load placed on a beam is best described as a force that
(a)
(b)
(c)
(d)
34.
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.
35.
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)
(b)
(c)
(d)
is applied at regular intervals along the beam.
results only from the self weight of the beam.
is applied uniformly along a part of the beam.
is applied at the mid and quarter points of the span of the beam.
15.2 mm.
14.1 mm.
12.2 mm.
11.4 mm.
36. The units of stress for a member of a structure with a tensile force in it are
MECHANICAL
45
ENGINEERING STUDIES
STAGE 3
(a)
kg m-2.
(b)
kg m2 s-2.
(c)kg2 m s.
(d)
kg m-1 s-2.
37. The following diagram shows a force (F) acting on a rectangular object.
37. The following diagram shows a force (F) acting on a rectangular object.
F
c
P
b
a
The
Themoment
momentofofthe
theforce
forceFFabout
aboutaapoint
pointPPisisbest
bestdescribed
describedby
by:
a.
(a)
b.
(b)
c.
(c)
(d)
d.
F *Fa× a.
F *Fb× b.
F *Fc× c.
× (a+b).
F *F(a+b)
See nextwith
page
38. If a ball with mass of 1 kg is thrown upwards
an initial velocity of 10 ms-1 to a height of
20 m before falling back to earth, its potential energy when at its highest point is close to:
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)
(b)
(c)
(d)
19.6 J.
30.4 J.
50.0 J.
69.6 J.
See next page
ENGINEERING
STUDIES
ENGINEERING
STUDIES
STAGE
3 3
STAGE
4446
MECHANICAL
MECHANICAL
Part Part
B: Extended
answer
B: Extended
answer
55%
55%(105
(105Marks)
Marks)
(4) questions.
Answer
all questions.
Write
answers
in the
spaces
This This
part part
has has
fourfour
(4) questions.
Answer
all questions.
Write
youryour
answers
in the
spaces
provided.
provided.
Spare
pages
included
at the
of this
booklet.
They
can
usedfor
forplanning
planningyour
your
Spare
pages
are are
included
at the
endend
of this
booklet.
They
can
bebeused
responses
and/or
as
additional
space
if
required
to
continue
an
answer.
responses and/or as additional space if required to continue an answer.
• Planning:
If you
spare
pages
planning,indicate
indicatethis
thisclearly
clearly at
at the
the top
top of
● Planning:
If you
useuse
the the
spare
pages
forfor
planning,
of the
the page.
page.
•
Continuing
an
answer:
If
you
need
to
use
the
space
to
continue
an
answer,
indicate
in the
● 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
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.
number of the question that you are continuing to answer at the top of the page.
Suggested working time: 110 minutes.
Suggested working time: 110 minutes.
Question 39
Question 39
(25 marks)
(25 marks)
The following
diagram
a and
ropepulley
and pulley
system
for unloading
boxes
a truck
The diagram
below
shows show
a rope
system
for unloading
boxes
fromfrom
a truck
andand
placing
them
on
the
ground
where
they
can
be
unpacked.
The
top
pulley-block
is
attached
to
placing them on the ground for unpacking. The top pulley-block is attached to the end of a beam
the
end
of
a
beam
that
is
supported
at
one
end
on
the
wall
of
the
factory
unit
and
by
a
tie
rod
at
that is supported at one end on the wall of the factory unit and by a tie rod at the other end.
the other end.
2.0 m
Tie
30º
Beam
30º
F
200 kg
See next page
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 where the pulley system is attached are:
●
●
Vertical force - close to 2384 N
Horizontal force - close to 245 N.
Show all workings. (8 marks)
See next page
ENGINEERING STUDIES
STAGE 3
46
MECHANICAL
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 A is 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
ENGINEERING
an arrow, clearly
indicating its direction, and
value or a
STUDIES
48 label each force with its knownMECHANICAL
STAGE
blank
(5 marks)
3 if its value is currently unknown.
(c)
Draw on the following diagram of the beam a schematic representation of the forces
resulting from all the applied loads and reactions. Point A is 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 label if its value is currently
unknown.
(5 marks)
A
(d)
B
C
Show that the force in the tie rod is close to 5748 N.
(4 marks)
_________________________________________________________________________
_________________________________________________________________________
(d)
Show that the force in the tie rod is close to 5748 N. (4 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
See next page
MECHANICAL
(e)
47
ENGINEERING STUDIES
STAGE 3
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
STAGE 3
ENGINEERING STUDIES
STAGE
3
Question
40
50
MECHANICAL
48
MECHANICAL
(25 marks)
Question 40
(25 marks)
The following diagram shows a cross section and a partial elevation of a cantilevered balcony.
The The
diagram
below
shows a cross-section
and a partial
elevation
of aon
cantilevered
balcony.
balcony
is intended
to support a number
of people
standing
it. The main
beamsThe
are
balcony
is intended
to the
support
the weight
number
of people
standing
on it. The
main the
beams
cantilevered
from
wall and
spacedofata2.0
m intervals.
Four
cross beams
support
are cantilevered
and spaced at 2.0 m intervals. Four cross beams support the
decking that from
is 50the
mmwall
thick.
decking, which is 50 mm thick.
Decking
Cross Beam
Cantilever Beam
2.0 m
3.0m
Elevation
Elevation
Cross Section
Cross-section
The material and loading properties are:
The material and loading properties are:
Item
Component
Cantilever Beam
Cantilever beam
Cross Beam
Cross beam
-3
900
kg m-3
900 kgm
Decking Decking
People
Weight/Load
Weight/Load
200 kgm-1
200 kg m-1
-1
50 kgm
50 kg m-1
500 kg m-2
500 kgm-2
People
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
For the design you can assume that each cantilevered beam carries the loads from a 2.0 m
standing on the balcony, from that part of the decking equidistant from each adjacent cross
length of balcony. Also, each cross beam carries a share of the loads imposed from the
beam.
decking, and the people standing on the balcony, from that part of the decking equidistance
from each adjacent cross beam.
(a)
Show that the load imposed on the balcony by the people and the weight of the decking
(a)is about
Show
thatNthe
load
themarks)
decking
5341
m-2-2
. imposed on the balcony by the people and the weight of (3
is it is about 5341 Nm
(3 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
See next page
See next page
MECHANICAL
51
MECHANICAL
49
ENGINEERING STUDIES
STAGE 3
ENGINEERING STUDIES
STAGE 3
(b)
Show that the loads imposed by the four cross beams (that support the decking and the
peopleShow
on the
balcony)
on imposed
the cantilever
are approximately
as follows:
(b)
that
the loads
by thebeam
four cross
beams that support
the decking and the
people on the balcony on the cantilever beam are approximately as follows.
(5 marks)
11
662 N
662 NN
11662
N 11
11662
6321 N
6321 N
(5 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
See next page
See next page
ENGINEERING STUDIES
STAGE 3
ENGINEERING
STUDIES
Question
40 (continued)
STAGE 3
50
52
MECHANICAL
MECHANICAL
(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
(c) diagrams
on themoment
diagrams.
(17on
marks)
Sketchand
the show
shearthese
force values
and bending
diagrams for the cantilever beam
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
BM
See next page
See next page
MECHANICAL
MECHANICAL
53
51
Question
41
Question
41
MECHANICAL
ENGINEERING STUDIES
ENGINEERING STUDIES
STAGE 3
STAGE 3
(25
marks)
(25
marks)
ENGINEERING
STUDIES
STAGE 3
The diagram below shows a schematic representation of a railway wagon on a track
Question
(25 marks)
approaching
an41
energy absorbing buffer stop.
The following diagram show a schematic representation of a railway wagon on a track
approaching an energy absorbing buffer stop.
53
The following diagram show a schematic representation of a railway wagon on a track
approaching an energy absorbing buffer stop.
The railway wagon weighs 5000 kg when fully loaded and is potentially moving at up to 20 kph.
The
railway
5000onkgthe
when
fullyfail
loaded
and isstop
potentially
moving
at up to
to rest
The
idea iswagon
that if weighs
the brakes
wagon
the buffer
will bring
the wagon
If the
brakes
on the wagon fail, the buffer stop is intended to bring the wagon to rest
20without
km h–1.any
major
damage.
without any major damage.
The
railway
weighs
5000
kg when fullyram
loaded
is potentially
moving
at up to 20
The
buffer
stopwagon
is made
up from
a compressible
withand
a very
large spring
all contained
in akph.
large
The ram
linearlyfail
elastic
response
to an
imposed
force.toThe
Theblock
ideaof
is concrete.
that if the brakes
onhas
theawagon
the buffer
stop will
bring
the wagon
rest
The
buffer
stop
up of
a compressible
ram with a very large spring contained in a large
characteristics
ofmade
the damage.
ram
are
like this:
without
anyismajor
block of concrete. The ram has a linearly elastic response to an imposed force. The
The bufferofstop
made
a compressible
ram with a very large spring all contained in a
characteristics
theisram
are up
as from
shown
in the graph below:
Force The ram has a linearly elastic response to an imposed force. The
large block of concrete.
characteristics of the ram are like this:
Force
250 kN
Force (kN)
250250
kN
500 mm
Change
in length
where the Change in Length (the horizontal axis) is a measure of how much the ram moves,
500mm
and Force (the vertical axis) is the force required to make500
the
movement.Change
The slope of this
length
graph is called the stiffness of the ram. You can assume that the buffer in
stop
is heavy enough
Change
in length (mm)
that it will not move when impacted by the
wagon.
where the Change in Length (the horizontal axis) is a measure of how much the ram moves,
and Force (the vertical axis) is the force required to make the movement. The slope of this
The change
lengththe
(horizontal
axis)
a measure
ofassume
how much
moves
force enough
graph isincalled
stiffness of
theisram.
You can
thatthe
theram
buffer
stopand
is heavy
(vertical
themove
forcewhen
required
to make
The slope of this graph is called the
thataxis)
it willisnot
impacted
by the
the movement.
wagon.
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
See next page
See next page
ENGINEERING STUDIES
STAGE 3
52
MECHANICAL
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 h–1 is
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 comes 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-2 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
STAGE 3
54
MECHANICAL
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
Question 42 ENGINEERING STUDIES
STAGE 3
(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)Describe two (2) properties of stainless steel that make it suitable for use in external
environments.
(2 marks)
One:
Two:
(b)
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:
(c)
When was it reported in the press that stainless steel was invented, and for what use?
(2 marks)
When:
Use:
(d) Complete the following sentences.
To be protective, the corrosion 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
(3 marks)
ENGINEERING STUDIES
STAGE 3
56
MECHANICAL
Question 42 (continued)
(e)
In harsh environments what percentage of chromium is recommended for stainless steel?
(1 mark)
(f)
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:
(g)Name five (5) common applications for stainless steel. (5 marks)
One:
Two:
Three:
Four:
Five:
(h)
Name one notable Australian application of stainless steel and how much was required
to build it.
(2 marks)
(i)
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
(j)
57
ENGINEERING STUDIES
STAGE 3
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
Use stainless steel?
(yes/no)
Handrails on
external
stairways
Piping in
desalination
plants
Boxes for
desktop
computers
End of Section Two: Mechanical
See next page
Reason
ENGINEERING STUDIES
58
This page has been left blank intentionally
See next page
STAGE 3
ELECTRONIC/ELECTRICAL
59
Section Two: Specialist field—Electronic/Electrical
ENGINEERING STUDIES
STAGE 3
65% (115 Marks)
This section has two (2) parts.
Part A:
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 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.
If 0.47 µF, 0.22 µF and 0.1 µF capacitors are connected in series, the overall capacitance value is approximately
(a)
(b)
(c)
(d)
45.
On the schematic symbol of a NPN transistor, the arrow points
(a)
(b)
(c)
(d)
0.06 µF.
0.79 µF.
16.67 µF.
0.013 µF.
inward on the base lead.
outward on the collector lead.
inward on the emitter lead.
outward on the emitter lead.
See next page
ENGINEERING STUDIES
STAGE 3
60
ELECTRONIC/ELECTRICAL
46.
Assuming that the cost of electricity is 20 cents per kWh, approximately how long can
you operate a 200 W television for $1?
(a)
(b)
(c)
(d)
47.
An instrument used for measuring potential difference is called
(a)
(b)
(c)
(d)
48.
To measure a circuit’s source voltage, the voltmeter must
(a)
(b)
(c)
(d)
49.
In a series resistive circuit, the smallest amount of power is dissipated by the
(a)
(b)
(c)
(d)
50.
A particular capacitor stores 60 µC of charge when 12 V are applied across its plates. What is its capacitance value?
(a)
(b)
(c)
(d)
51.
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 secondary load?
(a)
(b)
(c)
(d)
5 hours
10 hours
25 hours
40 hours
an ammeter.
an ohmmeter.
a potentiometer.
a voltmeter.
have the black lead toward the positive side of the source.
be placed in series in the circuit.
be placed across the source.
only be used when the source is switched off.
first resistor.
last resistor.
resistor with the highest resistance.
resistor with the lowest resistance.
0.2 µF
5 µF
60 µF
720 µF
24 V
60 V
120 V
600 V
See next page
ELECTRONIC/ELECTRICAL
61
ENGINEERING STUDIES
STAGE 3
52.
A transistor has a collector current IC of 10 mA. How much is the base current IB if the transistor has a β of 200?
(a)
(b)
(c)
(d)
50 µA
20 mA
0.5 A
2A
See next page
ENGINEERING STUDIES
ELECTRICAL/ELECTRONIC
STAGE 3
61
62
ELECTRONIC/ELECTRICAL
ENGINEERING
STUDIES
STAGE 3
B: Extended
answer
Part Part
B: Extended
answer
Marks)
55% 55%
(105 (105
Marks)
This This
part has
(4) questions.
Answer
all questions.
Write
youryour
answers
in the
partfour
has four
(4) questions.
Answer
all questions.
Write
answers
in spaces
the spaces
provided.
provided.
SpareSpare
pagespages
are included
at theat
end
thisofbooklet.
They They
can be
used
planning
your your
are included
theofend
this booklet.
can
be for
used
for planning
responses
and/or
as additional
spacespace
if required
to continue
an answer.
responses
and/or
as additional
if required
to continue
an answer.
• Planning:
If youIfuse
the
spare
pages
for
planning,
indicate
this
clearly
at the top
of the
● Planning:
you use the spare pages for planning, indicate this clearly
at the
top page.
of the page.
• Continuing
an
answer:
If
you
need
to
use
the
space
to
continue
an
answer,
indicate
in the in the
● Continuing an answer: If you need to use the space to continue an answer, indicate
original
answer
spacespace
wherewhere
the answer
is continued,
i.e. give
page
Fill in the
original
answer
the answer
is continued,
i.e.the
give
thenumber.
page number.
Fill in the
number
of theofquestion(s)
thatthat
youyou
areare
continuing
to answer
at the
top top
of the
number
the question
continuing
to answer
at the
of page.
the page.
Suggested
working
time:time:
110 110
minutes.
Suggested
working
minutes.
Question 53
Question 53
(25 marks)
(25 marks)
A DC voltage source of unknown voltage value VS is applied across a resistor network, as shown
A DC voltage source of unknown voltage value VS is applied
across a resistor network, as
in the circuit diagram below, where R1 = 1 kΩ, R2 = 2 kΩ, R3 = 1 kΩ, and R4 = 1 kΩ.
shown in the circuit diagram below, where R1 = 1 kΩ, R2 = 2 kΩ, R3 = 1 kΩ, and R4 = 1 kΩ.
Ii1
1
R1
V2 R2
VS
R3
R4
RT
(a)
Determine the value of the total resistance RT, which is the equivalent resistance value
(a)
Determine the value of the total resistance R , which is the equivalent resistance value
seen by the voltage source. Show all workings. T
seen by the voltage source. Show all workings.
(3 marks)
(3 marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
Seepage
next page
See next
ELECTRONIC/ELECTRICAL
63
ENGINEERING STUDIES
STAGE 3
(b) Given that the source voltage is set to a value such that the resistor R4 is dissipating
100 mW of power, calculate the values for the voltage V2, the current I1 and the source
voltage VS. Show all workings.
(i)Voltage V2
(2 marks)
(ii)Current I1
(4 marks)
(iii)
(4 marks)
Source voltage VS
See next page
ENGINEERING STUDIES
STAGE 3
64
ELECTRONIC/ELECTRICAL
Question 53 (continued)
(c)
Consider the following two separate scenarios:
(i)
If the resistor R1 was replaced by another resistor of lesser resistance value
(while all other circuit elements remained unchanged), how would this affect the
total resistance RT and the current I1?
Tick the appropriate boxes below and provide a reason for each.
The total resistance RT would:
●
increase
●
decrease
●
remain unchanged.
Reason:
The current I1 would:
●
increase
●
decrease
●
remain unchanged.
Reason:
See next page
(4 marks)
ELECTRONIC/ELECTRICAL
65
ENGINEERING STUDIES
STAGE 3
(c)
(ii)
If the source voltage was increased in value (while all other circuit elements
remained unchanged), how would this affect the total resistance RT and the
current I1?
Tick the appropriate boxes below. There is no need to show your workings.
(4 marks)
The total resistance RT would:
●
increase
●
decrease
●
remain unchanged.
Reason:
The current I1 would:
●
increase
●
decrease
●
remain unchanged.
Reason:
See next page
ENGINEERING STUDIES
STAGE 3
66
ELECTRONIC/ELECTRICAL
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 i1 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 RT correctly.
(2 marks)
See next page
ENGINEERING STUDIES
STAGE 3 ENGINEERING STUDIES
STAGE 3
ELECTRONIC/ELECTRICAL
Question 54
Question 54
66
66
ELECTRICAL/ELECTRONIC
ELECTRICAL/ELECTRONIC
67
ENGINEERING(25
STUDIES
marks)
STAGE (25
3 marks)
Question
54
(25 on
marks)
The following
figure shows a basic “dark sensor” circuit that uses the transistor to switch
the
The
following
figure
shows
a
basic
“dark
sensor”
circuit
that
uses
the
transistor
to
switch
on the
Light Emitting Diode (LED) when there is a lack of incident light on the Light Dependent
The
figure
below
shows
a
basic
‘dark
sensor’
circuit
that
uses
a
transistor
to
switch
on
the
light
Light Emitting
Diodethe
(LED)
there is aby
lack
incident light
the Light
Dependent
Resistor (LDR).
Conversely,
LED when
is deactivated
theoftransistor
whenonthere
is sufficient
emitting
(LED)
whenConversely,
there is a lack
incident
light on the
dependentwhen
resistor
(LDR).
Resistor
theofLED
is deactivated
bylight
the transistor
there
is sufficient
incident diode
light
on
the(LDR).
LDR.
Conversely,
the LED
is on
deactivated
incident
light
the LDR. by the transistor when there is sufficient incident light on the
LDR.
VS
VS
R3
R1
R1
D
Q
R2
0V
(a)
(a)
R3
D
Q
R2
0 “Dark
V‘DarkSensor”
sensor’ Circuit
circuit
“Dark Sensor” Circuit
The left part of the above “dark sensor” circuit is a voltage divider module as shown in
The
left
part
of left
theSuppose
above
‘dark
is a and
voltage
module,
shown
The
part
of the
circuit
a voltage
divider
module
as shown in
=sensor’
6 V,“dark
R1circuit
= sensor”
10 kΩ,
theisdivider
resistance
of
theas
LDR,
R2, in
the(a)
figure
below.
VSabove
=
6
V,
R
=
10
kΩ
and
the
resistance
of
the
LDR,
R
,
ranges
the
figurefrom
below.
Suppose
=
6
V,
R
=
10
kΩ,
and
the
resistance
of
the
LDR, R2,
the100
figure
below.
Suppose
V
ranges
Ω in
veryVbright
light
to
200
kΩ
in
the
dark.
Note
that
an
LDR
is
a
S
1 S
2
1
ranges
from
100
Ω
in
very
bright
light
to
200
kΩ
in
the
dark.
Note
that
an
LDR
is a
from
100
Ω
in
very
bright
light
to
200
kΩ
in
darkness.
Note
that
an
LDR
is
a
resistor
resistor whose resistance increases with decreasing intensity of incident light.
resistor
whose resistance
increases
with decreasing
whose
resistance
with decreasing
of incident
light. Therefore,
in light.
the Therefore,
in the increases
voltage
divider
module,
theintensity
output
voltage
VO intensity
varies
asofRincident
2 changes.
Therefore,
in the output
voltagevoltage
divider Vo
module,
voltage VO varies as R2 changes.
voltage divider
module,
variesthe
as output
R2 changes.
VS
VS
R1
R1
VO
R2
0V
VO
R2
0V
End of questions
End of questions
See next page
ENGINEERING STUDIES
STAGE 3
68
ELECTRONIC/ELECTRICAL
Question 54 (continued)
(a)
(i)
By using the voltage division principle, write a mathematical expression for VO in
terms of R1, R2, and VS.
(2 marks)
(ii)
Show that VO swings from 59.4 mV to 5.71 V.
(2 marks)
(iii)
Calculate the value for R2 such that VO = 0.7 V. Show all workings.
(2 marks)
(iv)
Suppose a 4-band colour coded resistor of 10 kΩ with 5% tolerance is used to
implement R1. 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
(b)
69
ENGINEERING STUDIES
STAGE 3
Suppose the above ‘dark sensor’ circuit has the following parameters.
Parameters
Source voltage, VS
6V
Resistor R3
220 Ω
LED on-voltage VLED,on
2V
Transistor on-voltage VBE,on
0.7 V
Transistor saturation voltage VCE,sat
0V
Transistor current gain β
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)
the transistor is operating in the cut-off region. Show all workings.
(ii)
See next page
(2 marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
ENGINEERING
STUDIES
70
ELECTRONIC/ELECTRICAL
STAGE______________________________________________________________________
3
Question 54 (continued)
(c)
(c)
Instead of one LED, suppose the above ‘dark sensor’ circuit is now required to drive
Instead of one LED, suppose the above “dark sensor” circuit is now required to drive a
a cluster of 4 LEDs in a 2-by-2 array. The figure below shows such a light module in
cluster of 4 LEDs in a 2-by-2 array. The figure below shows such light module in
isolation
that each
isolation from
from the
the rest
rest of
of the
the circuit.
circuit. This
This module
module is
is designed
designed so
in such
a wayLED
thatoperates
each
at
a
forward
voltage
of
2.2
V
and
a
current
of
16
mA.
LED operates at a forward voltage of 2.2 V and a current of 16 mA.
R
D
D11
D2
D2
R
D3
D3
D4
D4
Vss = 6 V
(i)
(i)
Determine the required value for resistor R. Show all workings.
Determine the required value for resistor R. Show all workings.
(4 marks)
(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
See next page
ELECTRONIC/ELECTRICAL
71
ENGINEERING STUDIES
STAGE 3
(iii)
If the LED D1 was faulty and behaved like an open circuit, how would this affect
D3?
Tick the appropriate box below and explain your answer.
The LED D3 would be:
●
the same in brightness
●
brighter
●
dimmer
●
off.
Explanation:
See next page
(3 marks)
ELECTRICAL/ELECTRONIC
71
ENGINEERING STUDIES
STAGE 3
Question 55
Question 55 ENGINEERING STUDIES
STAGE 3
ELECTRONIC/ELECTRICAL
72
(25 marks)
(25 marks)
Consider
which
has
a transformer
and
a rectifier
connected
in between
between an
anAC
Considerthe
thefollowing
followingcircuit
circuit,
which
has
a transformer
and
a rectifier
connected
AC
source
and
a load.
Assume
switch
is initially
open.
source
and
a load.
Assume
thethe
switch
is initially
open.
Is
II pP
IS
+
+
VP
VS
-
-
switch
C
+
VL
RL
-
8:1
AC Source
(a)
(a)
Transformer
Rectifier
Load
Suppose
Supposean
anideal
idealtransformer
transformerisisused.
used.Calculate
Calculate
(i)
the secondary voltage VS of the transformer in the case when the primary
voltage
(i)
the
secondary
voltage
S of the
voltage
VP = 240
VAC.VShow
alltransformer
workings. in the case when the primary (2
marks)
VP = 240 VAC. Show all workings.
(2 marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
(ii)
the primary current IP of the transformer in the case when the secondary current
= 0.3
AAC.current
Show all
workings.
(ii) ISthe
primary
IP of
the transformer in the case when the secondary current IS = 0.3 A AC. Show all workings.
marks)
(2 (2
marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
See next page
See next page
25
0
-25
0
5
10
ELECTRONIC/ELECTRICAL
ENGINEERING
STUDIES
-50
STAGE 3
15
72
20
25
73
30
35
40
ENGINEERING STUDIES
ELECTRICAL/ELECTRONIC
STAGE 3
t (ms)
V voltage
min
(b)(b) Suppose
thethe
diode
used
in the
has ahas
forward
voltage
of 0.6of
V,0.6
theV,
resistor
Suppose
diode
used
in rectifier
the rectifier
a -42.43
forward
the resistor
R
=
100
Ω,
the
switch
is
open,
and
the
waveform
of
the
secondary
voltage
V
L
S is as
RL = 100 Ω, the switch is open and the waveform of the secondary voltage
VS is as
shown
below.
shown below.
(i)
Clearly sketch the waveform and label its maximum and minimum voltage values
for the primary voltage VP.
Secondary voltage V
S
Secondary
Voltage VS
42.43 V max
42.43 V max
(3 marks)
Primary Voltage VP
Vs (V) 50
VS (V)
V P (V) 50
25
25
0
0 0
-25 0
–25
-50
–50
5
5
10
10
15
15
20
20
25
30
25
30
35
35
40
40
t (ms)
t (ms)
-42.43 V min
– 42.43 V min
(i) (i) Clearly
sketch
the waveform
and and
labellabel
its maximum
and minimum
voltage
valuesvalues
Sketch
the waveform
clearly
its maximum
and minimum
voltage
for for
thethe
primary
voltage
VP. VP.
primary
voltage
(3 marks)
(3 marks)
Primary voltage Vp
Primary Voltage VP
VP (V)
V P (V)
0
5
End
10 of questions
15
20
ELECTRICAL/ELECTRONIC
73
25
t (ms)
30
35
40
ENGINEERING STUDIES
STAGE 3
Sketch
the the
waveform
clearly
and label
its maximum
and minimum
(ii) (ii) Clearly
sketch
waveform
and label
its maximum
and minimum
voltagevoltage
values values
for
the
load
voltage
V
.
Assume
no
reverse
breakdown
of
the
diode.
(3 marks)
for the load voltage VL. L
(3 marks)
Load Voltage
VL
Load voltage
VL
VL (V)
V L (V)
0
5
10
15
20
25
30
35
40
t (ms)
End of questions
(iii)
See
next
Clearly sketch the waveform and
label
its page
maximum and minimum voltage values
for the load voltage VL when the diode is connected in reverse by mistake (i.e.
when the diode’s anode and cathode are swapped around).
ENGINEERING STUDIES
STAGE 3
74
t (ms)
ELECTRONIC/ELECTRICAL
Question 55 (continued)
(iii)
(iii)
Clearly sketch the waveform and label its maximum and minimum voltage values
for the load voltage VL when the diode is connected in reverse by mistake (i.e.
Sketch the waveform clearly and label its maximum and minimum voltage values when the diode’s anode and cathode are swapped around).
for the load voltage VL when the diode is connected in reverse by mistake,
(3 marks)
i.e. when the diode’s anode and cathode are swapped around.
(3 marks)
Diode
is Connected
in Reverse
Load
Voltage
VL when
Load
voltage
V when
diode
is connected
in reverse
L
VL (V)
V L (V)
0
5
10
15
20
25
30
35
40
t (ms)
(iv)
(iv)
Calculate the frequency of VP. Show all workings.
(2 marks)
Calculate the frequency of VP. 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
See next page
ELECTRONIC/ELECTRICAL
75
ENGINEERING STUDIES
STAGE 3
(c)
Suppose the switch is closed and the capacitor of 1000 µF now becomes part of the
circuit.
(i)
Explain what primary effect this capacitor has on the load voltage waveform.
(2 marks)
ELECTRICAL/ELECTRONIC
75
ENGINEERING STUDIES
STAGE 3
(ii)
With refer to the capacitor network as shown below, calculate the value of
(ii)
Withcapacitor
referenceCto
the capacitor
network shown
calculate
of Show
as the equivalent
overall below,
capacitance
is Cthe
1000 µF.
2 such
T = value
all
workings.
capacitor C2 such that the equivalent overall capacitance is CT = 1000 µF.
Show all workings.
(4 marks)
(4 marks)
C2
C
2
C
CTT = 1000 µF
C11 = 600 µF
C33 = 600 µF
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
(iii) ______________________________________________________________________
What is 1000 µF in nanofarad (nF)?
(2 marks)
(iii)
What is 1000 µF in nano-Farad (nF)?
(2 marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
See next page
ENGINEERING STUDIES
STAGE 3
ENGINEERING STUDIES
STAGE
3 56
Question
76
ELECTRICAL/ELECTRONIC
76
ELECTRONIC/ELECTRICAL
(30 marks)
Question 56 (30 marks)
A circuit is constructed as shown below, with five resistors 𝑅𝑅1 = 2 kΩ, 𝑅𝑅2 = 2 kΩ, 𝑅𝑅3 = 6 kΩ,
A𝑅𝑅circuit
is constructed
resistors
R112
=2 VkΩ,
R2𝑉𝑉=2
kΩ, R4stated
=6 kΩ,
3=6
and 𝑅𝑅5 = 4 as
kΩ,shown
a fusebelow,
F, andwith
two five
batteries
𝑉𝑉𝑆𝑆1 =
and
= 16RV.
Unless
4 = 6 kΩ,
𝑆𝑆2 kΩ,
and
R
=4
kΩ,
a
fuse
F,
and
two
batteries
V
=12
V
and
V
=16
V.
Unless
stated
otherwise,
the
5
S1
S2
otherwise, the fuse is behaving like a short circuit with zero resistance (i.e. zero voltage drop).
fuse
is behaving
like
shorttocircuit
zero of
resistance
voltage
An ideal
An ideal
ammeter
is aused
obtainwith
reading
𝑖𝑖𝑆𝑆1 = 3.75(zero
mA and
𝑖𝑖𝑆𝑆2 =drop).
4.25 mA.
The ammeter
diagram is
used
obtain
readings
IS1=3.75ofmA
IS2=4.25
The diagram
below
alsocircuit
specifies
the
belowtoalso
specifies
theofdirection
theand
current
and mA.
the voltage
polarity
of each
element.
direction of the current and the voltage polarity of each circuit element.
F
V1
R1
Ii11
VS1
IiS1
S1
Ii3
V5 R5
B
A
VS2
V3 RR3
V4 R4
IiS2
S2
Ii5
Ii44
V2
R2
Ii22
(a)
(a)
Use the Kirchhoff’s current law to determine the value for the current IAB, which is the
is marks)
the
Use thethat
Kirchhoff’s
current
determine
theall
value
for the current 𝑖𝑖𝐴𝐴𝐴𝐴 , which (2
current
flows from
Nodelaw
A totoNode
B. Show
workings.
current that flows from Node A to Node B. Show all workings.
(2 marks)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
End of questions
See next page
ELECTRONIC/ELECTRICAL
(b)
77
ENGINEERING STUDIES
STAGE 3
Knowing that the power dissipated by the resistor R5 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)
I1 =
I2 =
I3 =
I4 =
I5 =
(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)
V1 =
V2 =
V3 =
V4 =
V5 =
See next page
ENGINEERING STUDIES
STAGE 3
78
ELECTRONIC/ELECTRICAL
Question 56 (continued)
(d)
Calculate the total power supplied by the two batteries. Show all workings.
(e)
Suppose the fuse F is blown.
(i)
Show that the equivalent resistance value as seen by the battery VS2 with the
fuse F blown is 5.75 kΩ.
(4 marks)
(ii)
Calculate the new value for the current IS2 when the fuse F is blown. Show all
workings.
(2 marks)
End of Section Two: Electronic/Electrical
End
questions
Seeofnext
page
(2 marks)
STAGE 3
79
Additional working space
See next page
ENGINEERING STUDIES
ENGINEERING STUDIES
80
Additional working space
See next page
STAGE 3
STAGE 3
81
Additional working space
See next page
ENGINEERING STUDIES
ENGINEERING STUDIES
82
Additional working space
See next page
STAGE 3
STAGE 3
83
See next page
ENGINEERING STUDIES
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
Question 13
Text adapted from: Berrill, T., & 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/ConsumerInfo/SWHguide.html.
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