ELT315114 Part 1 - Department of Education · · 2017-07-21electronic circuit. (2 marks) ... (2 marks) Question 10 continues. Electronics – Part 1 Page 15 ... likely behaviour

Pages: 24 Questions: 15 ©Copyright for part(s) of this examination may be held by individuals and/or organisations other than the Tasmanian Qualifications Authority.

PLACE LABEL HERE

Tasmanian Certificate of Education

ELECTRONICS

Senior Secondary

Subject Code: ELT315114

External Assessment

2014

Part 1

Time: approximately 90 minutes

On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the course statement: Criterion 1 Apply knowledge and skills in designing, testing, building, and

experimenting with circuits. Criterion 4 Apply knowledge and understanding of digital and analogue

circuits and their components.

Section Total C1

C4

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AN

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S A

UT

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Electronics – Part 1

Page 2

CANDIDATE INSTRUCTIONS You MUST make sure that your responses to the questions in this examination paper will show your achievement in the criteria being assessed. Answer ALL questions. Answers must be written in the spaces provided on the examination paper. It is recommended that you spend approximately: 45 minutes on Section A 45 minutes on Section B Note: When candidates are asked to ‘show that’ an answer to a question is ‘about’ a numerical value given to one or two significant figures: • A candidate should provide their own answer to three significant figures (unless told otherwise

in that question). • A candidate whose answer rounds off to the given answer should continue to use their own three

significant figure answer in any subsequent questions requiring this answer. • A candidate whose answer is significantly different from that given by the examiner should use

the one or two significant figure answer given by the examiner in answering subsequent questions.

The 2014 External Examination Information Sheet for Electronics can be used throughout the examination. No other written material is allowed into the examination. A spare set of diagrams has been provided in the back of the answer booklet for you to use if required. If you use the spare diagrams, you MUST indicate you have done so in your answer to that question.


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This section assesses Criterion 1. Answer ALL questions from this section. Question 1 (a) Sketch a simple circuit with: (2 marks)

• a power supply • a resistor • a voltmeter • an ammeter

(b) Which would be easier to use in trouble-shooting an electronic circuit: a voltmeter or an

ammeter? Give one reason. (2 marks) ............................................................................................................................................. .............................................................................................................................................

............................................................................................................................................. .............................................................................................................................................

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SECTION A

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Question 2 CMOS ICs have very high input impedance whereas TTL ICs have fairly low input impedance. Small amounts of static electricity on plastic and other insulating materials can cause very high voltages to be present. These high voltages can potentially damage or destroy some ICs. (a) (i) Which type of IC is more likely to be damaged by static electricity? (1 mark) .................................................................................................................................... (ii) Why? (1 mark) .................................................................................................................................... .................................................................................................................................... (b) State two precautions that should be taken when handling and using the IC type you

selected in part (a). (2 marks) 1. ........................................................................................................................................ ............................................................................................................................................. 2. ........................................................................................................................................

.............................................................................................................................................

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Question 3 (a) Two devices that can cut off the power supply are a fuse and an RCD (residual current

device). One of these is mainly intended to protect the appliance, the other for human safety. Which device fulfils each function? Justify your answers. (3 marks)

protect the appliance .......................................................................................................... ............................................................................................................................................. .............................................................................................................................................

human safety ......................................................................................................................

............................................................................................................................................. ............................................................................................................................................. (b) Electronic devices may run from the mains by using a combination of the following:

transformers to step the voltage up or down, a rectifier, and capacitors to smooth current or store charge.

When such a device is disconnected from the mains, an electric shock hazard still exists

and precautions still need to be taken. (i) What is the source of this shock hazard? (1 mark) .................................................................................................................................... .................................................................................................................................... (ii) Explain carefully how a technician should safely eliminate this shock hazard

before working on such a device. (2 marks) .................................................................................................................................... ....................................................................................................................................

.................................................................................................................................... ....................................................................................................................................

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Question 4 An ECG detects electrical signals within the body to interpret the heart’s behaviour. Below is a diagram of a proposed circuit for an ECG amplifier.

ECG Amplifier (a) Three operation amplifiers (op amps) are used in the design, with each operating in a

different mode. Identify the modes of the two labelled op amps. (2 marks) op amp 1 ............................................................................................................................ ............................................................................................................................................. op amp 2 ............................................................................................................................ ............................................................................................................................................. (b) As this device is intended to be connected to the body, elimination of hazards is

essential.

Outline two potential hazards with this device, in design or in use, and how you could

minimise each of them. (4 marks) 1. ........................................................................................................................................ ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. 2. ........................................................................................................................................ ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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1 2


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Question 5 You have been given the task of designing a seatbelt warning alarm for the two front seats of an older car. The alarm is to sound when the following conditions are all met. • The ignition is switched on. • The driver is seated but the seatbelt is not fastened. • If a passenger is seated but the seatbelt is not fastened. Input signals are generated from ignition, seat and seatbelt sensors. The output of these sensors is logic HIGH when: • The ignition is on. • A seat is used. • A seatbelt is fastened. (a) Design a block diagram of your proposed circuit. (4 marks) (b) Explain what components you would use in your design. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 6 The circuit diagram below is for an amplifier that uses a dual voltage power supply.

(a) Calculate the voltage gain of the amplifier. (1 mark) ............................................................................................................................................. ............................................................................................................................................. (b) When fed into an oscilloscope, the input signal produced the following display:

Question 6 (b) continues.

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1 ms per cm

20 m

V pe

r cm


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Question 6 (b) (continued) (i) What is the frequency of the signal? (1 mark) .................................................................................................................................... .................................................................................................................................... (ii) The other channel of the oscilloscope was then connected to the output of the

amplifier. Sketch the expected oscilloscope display, indicating clearly the vertical scale used. (The oscilloscope is still triggered by the input signal.) (2 marks)

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Question 7 Using the design below, a student constructed a circuit for a device in a garage that assists parking. In this design, IC1 is a 555 oscillator which pulses D1, an Infra-Red LED. The emitted IR signal reflects from the garage wall and is detected by D2, a photo-diode. The LEDs D5, D6 and D7 are driven by the comparators. When the car is about 20 cm from the wall, D7 lights, at 10 cm both D7 and D6 light, and at 5 cm all three LEDs light. The student constructed the circuit on a PCB. However, when switched on, none of the visible LEDs lit up. The circuit design itself, though, is known to be error-free. Using the table on the next page, outline, in order, the steps you would follow in trouble-shooting this construction. At least five steps should be given. Be sure to identify any testing devices used, such as oscilloscope, multimeter, continuity tester, logic probe or visual check. (10 marks)

Question 7 continues.

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Question 7 (continued)

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Step Test Testing Device

1

2

3

4

5

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Question 8 Software like Circuit Wizard™ can be used to simulate the behaviour of circuits. (a) What operations in Circuit Wizard, or similar electronics simulation software, allow input

and output voltages to be displayed? (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Give two limitations of Circuit Wizard in accurately representing the behaviour of an

electronic circuit. (2 marks) 1. ......................................................................................................................................... ............................................................................................................................................. 2. ......................................................................................................................................... .............................................................................................................................................

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This section assesses Criterion 4. Answer ALL questions from this section. Question 9 (a) (i) Complete this table of resistor values: (2 marks)

Value Band 1 Band 2 Band 3 Tolerance Orange White Black Red

560R ± 5%

(ii) In stating the resistance value as 560R ± 5%, what is the significance of the ± 5%? (1 mark) .................................................................................................................................... ....................................................................................................................................

.................................................................................................................................... (b) (i) Complete this table of capacitor values: (2 marks)

Code pF nF µF 150

332

(ii) Sketch how you would combine two capacitors with values 4µ7 and 1500 nF to

obtain maximum total capacitance. (1 mark)

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Question 10 (a) (i) Outline the fundamental difference between a passive filter and an active filter. (1 mark) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) State one relative advantage and one disadvantage of each type (other than cost). (2 marks)

Passive Active

Advantage

Disadvantage

(b) (i) With the aid of a labelled sketch graph, describe the effect of a low-pass filter on

incoming signals. (2 marks)

(ii) Using your graph, show how the cut-off or break frequency of a low-pass filter is

defined. (2 marks)



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Question 10 (continued) (c) Sketch a low-pass active filter incorporating RC filters in the input and feedback loop. (4 marks)

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Question 11 A student designed a circuit with an output driving a relay as shown in Diagram A. The instructor suggested the addition of another component as in Diagram B. By considering the properties of the two components RL1 and D1, describe and compare the likely behaviour of the two circuits. Circuit A (2 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... Circuit B (3 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... .......................................................................................................................................................

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A B

D1

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Question 12 An operational amplifier (op amp) is a differential amplifier. An ideal op amp has an open loop gain of infinity, an input impedance of infinity and an output impedance of zero. (a) Explain the meaning of the terms: (2 marks) differential amplifier .......................................................................................................... ............................................................................................................................................. open loop gain ................................................................................................................... ............................................................................................................................................. (b) Explain why it is desirable that the input impedance of an op amp be very high.

(1 mark) ............................................................................................................................................. ............................................................................................................................................. (c) Below is the graph of Voltage Gain ~ Frequency for a non-ideal op amp.

(i) What is the DC gain of this op amp? (1 mark) .................................................................................................................................... .................................................................................................................................... (ii) At what frequency does ‘unity gain’ occur (i.e. the gain is 1)? (1 mark) .................................................................................................................................... ....................................................................................................................................

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Op amp’s open loop frequency response


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Question 13 The Schmitt trigger is a useful circuit component which displays hysteresis. (a) By referring to the graph below, explain carefully the meaning of the term ‘hysteresis’ as

it applies to electronics. On the graph indicate the behaviour of the inverting Schmitt trigger pictured above, for both rising and falling input voltages. (3 marks)

Schmitt trigger response

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. A circuit diagram of an oscillator based on the above Schmitt trigger is given below. (b) On the graph of the output voltage ~ time given below, draw the curve of VX , the expected voltage at point X on the circuit. (2 marks)


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Question 13 (continued) (c) The circuit is modified as shown below. Describe the effect you would expect this modification to have on the oscillator. On the

axes below, sketch the new expected output voltage pattern. (The original output is already indicated.) (3 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. Original output

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/8 time

Vout


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Question 14 Consider the D-type flip-flop alongside and its associated Truth Table. (a) By referring to the Truth Table, answer each of the following, giving a brief explanation

for your each answer. (i) Is S active ‘Hi’ or active ‘Lo’? (1 mark) .................................................................................................................................... (ii) In Rows 4 and 5, what does ‘Nevermind’ indicate? (1 mark) .................................................................................................................................... (iii) Which is the synchronous input? (1 mark) .................................................................................................................................... (b) Show how to interconnect the appropriate pins of the D-type flip-flop below to convert

it into a T-type flip-flop. (1 mark)


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Clock Data (D) Reset (R) Set (S) Q ~ Q 1 ↑ 0 0 0 0 1

2 ↑ 1 0 0 1 0

3 ↓ Nevermind 0 0 No Change

4 Nevermind Nevermind 1 0 0 1 5 Nevermind Nevermind 0 1 1 0 6 Nevermind Nevermind 1 1 Disallows


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Question 14 (continued) (c) The circuit below can be used to synchronise a debounced switch with clock pulses. Complete the timing diagram for the Q and X outputs. (3 marks)

A

CLK

Q

X

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Question 15 Ripple counters and synchronous counters are two types of binary counter. However, one of these has a maximum operating speed which decreases as the number of binary digits increases. State which type will suffer from this and explain carefully the reason. (3 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... .......................................................................................................................................................

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SPARE DIAGRAMS

Question 6 (b) (ii)

Question 13 (c) (ii)

Question 14 (b)

time

Vout


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This question paper and any materials associated with this examination (including answer booklets, cover sheets, rough note paper, or information sheets) remain the property of the Tasmanian Qualifications Authority.

Pages: 28 Questions: 15 ©Copyright for part(s) of this examination may be held by individuals and/or organisations other than the Tasmanian Qualifications Authority.

PLACE LABEL HERE

Tasmanian Certificate of Education

ELECTRONICS

Senior Secondary


External Assessment

2014

Part 2

Time: approximately 90 minutes

On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the course statement: Criterion 5 Apply knowledge of digital and analogue systems in describing the

function and operation of components and circuits. Criterion 7 Apply knowledge and understanding of mathematical concepts in

electronics.

Section Total C5

C7

TA

SM

AN

IAN

QU

AL

IFIC

AT

ION

S A

UT

HO

RIT

Y


Page 2

CANDIDATE INSTRUCTIONS You MUST make sure that your responses to the questions in this examination paper will show your achievement in the criteria being assessed. Answer ALL questions. Answers must be written in the spaces provided on the examination paper. It is recommended that you spend approximately: 45 minutes on Section A 45 minutes on Section B Note: When candidates are asked to ‘show that’ an answer to a question is ‘about’ a numerical value given to one or two significant figures: • A candidate should provide their own answer to three significant figures (unless told otherwise

in that question). • A candidate whose answer rounds off to the given answer should continue to use their own three

significant figure answer in any subsequent questions requiring this answer. • A candidate whose answer is significantly different from that given by the examiner should use

the one or two significant figure answer given by the examiner in answering subsequent questions.

The 2014 External Examination Information Sheet for Electronics can be used throughout the examination. No other written material is allowed into the examination. A spare set of diagrams has been provided in the back of the answer booklet for you to use if required. If you use the spare diagrams, you MUST indicate you have done so in your answer to that question.


Page 3

This section assesses Criterion 5. Answer ALL questions from this section. Question 16 (a) Calculate the time constant of this RL combination. (1 mark) ............................................................................................................................................. ............................................................................................................................................. (b) What does the RL time constant describe? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (c) A 4.0 kHz wave has a period of 0.250 milliseconds. A 4.0 kHz square wave is fed into each of the following RL circuits as shown.

Sketch the expected output waveforms in each case. (4 marks)

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SECTION A

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/6


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Question 17 A counting chip may retain previous information even after power is turned off. When counting must start from zero, the chip needs to be reset at power-on. A common reset circuit is shown below.

(a) Is the reset input active ‘Hi’ or active ‘Lo’? Explain. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Describe how this reset configuration operates. You should include a sketch graph of

the voltage at the reset terminal at power-on. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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SW

C

R


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Question 18 A push-button switch was used to input data to a counter circuit as shown. However, the circuit did not function correctly, giving many ‘false’ counts. (a) State two possible faults in the circuit causing it to not function correctly. (2 marks) Reason 1: ............................................................................................................................ ............................................................................................................................................. Reason 2: ............................................................................................................................

............................................................................................................................................. (b) Sketch a circuit that will overcome both faults identified in part (a), if you can:

otherwise sketch a circuit overcoming a single fault. Explain how your circuit overcomes the fault(s). (3 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

............................................................................................................................................. .............................................................................................................................................

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Question 19 The plants in a greenhouse are to be protected from excessive sunlight. The relay in the circuit below will close a sunshade when the light intensity exceeds a certain level. The graph below illustrates how the resistance of the light sensor varies with light intensity. (a) At what light intensity will the relay activate? Show your reasoning. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


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Shade open

Shade closed


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Question 19 (continued) (b) Sketch a graph to show how the voltage across the relay will change with light intensity.

Include a scale. (2 marks) (c) How could the circuit be modified to operate a heat lamp when the light intensity drops

below 25 000 lux? Draw your schematic, showing component values. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. /7


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Question 20 In indoor slot-car racing, model cars run on parallel tracks. Below is a design to count how many laps are covered by each of two cars. The Hall sensors detect the cars as they pass the start/finish line. Some parts of the circuit referred to in the questions have been circled.

The design uses two dual BCD counters (4518), four BCD to 7-segment decoders (4511), four 7-segment displays and several other components. The questions on the next page are worth 1 mark each, a total of 10 marks.


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Question 20 (continued) (a) What is the purpose of the 100 µF capacitor at the top? ..................................................... ............................................................................................................................................. (b) Describe IC2. ....................................................................................................................... ............................................................................................................................................. (c) In what mode is IC5b operating? ......................................................................................... (d) When Pins 3 and 6 of IC1a go LO, what happens at Pin 10 of IC1b and what does this

do? .......................................................................................................................................

............................................................................................................................................. (e) What is the purpose of the 10k resistor connected to the reset switch S1? ............................................................................................................................................. ............................................................................................................................................. (f) What happens to the circuit when the switch S1 is pushed? ............................................... ............................................................................................................................................. ............................................................................................................................................. (g) On IC7, are the inputs LT and BL active? Explain. ........................................................... ............................................................................................................................................. ............................................................................................................................................. (h) What are two potential functions of IC2d? 1. ......................................................................................................................................... 2. .........................................................................................................................................

(i) What is the purpose of the 4.7 nF capacitor connected to the Hall sensor? ............................................................................................................................................. .............................................................................................................................................

(j) What is the size of the voltage supplied to the Hall sensor? ................................................

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Question 21 The monitoring system of a greenhouse has four inputs connected to four temperature sensors at different places: front, back, top and bottom. Its multiplexer selects the sensor from which to receive the temperature data. The selected temperature data is governed by the Select function (S1S0), which can have four values (002 to 112). The selected temperature data appears at the output q.

(a) The Select value 102 indicates S1 = 1 and S0 = 0. Which sensor will be selected by the

Select value 102? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) In order to select bottom what must the Select value be? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


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Select S1 S0

back

q

front

top

bottom


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Question 21 (continued) (c) What modification to the Select function would you need to allow for a fifth input? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 22 A speaker system comprises a ‘Tweeter’ handling high-frequency signals, a ‘Woofer’ handling the low-frequency signals and a ‘mid-range’ handling the signal frequencies in-between the others.

A cross-over filter system directs the various frequency signals to the appropriate speaker. Three suitable filters labelled A to C are shown below.

Filter

A

B

C


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Filter I

Filter II

Filter III

Input ~


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Question 22 (continued) (a) Is Filter C a High-Pass or a Low-Pass filter? Explain how you decided on your answer. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) In the spaces provided, match each speaker with its required filter (A, B or C). (2 marks)

(c) Why are these cross-over filters based on LC circuits rather than RC circuits? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Speaker Filter Tweeter

(High frequency)

Mid-range Woofer

(Low frequency)


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This section assesses Criterion 7. Answer ALL questions from this section. Question 23 In this question, you must show your working. (a) Convert 4E16 to decimal. (1 mark) ............................................................................................................................................. ............................................................................................................................................. (b) Convert 75410 to BCD. (1 mark) ............................................................................................................................................. ............................................................................................................................................. (c) Add 1001 00112 and 1 0101 11102, and then convert your answer to octal. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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SECTION B

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Question 24 The circuit for an audio power amplifier is shown below.

(a) Voltage gain may be expressed in decibels. If the amplifier’s input voltage is 1.5 mV rms and it gives an output of 12.0 V rms, show

that the voltage gain is approximately 80 dB. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Show that the maximum rms output voltage this amplifier can deliver without distortion

is approximately 21 V. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


8 ohms

+ 30 V

– 30 V

47 K


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Question 24 (continued) (c) What is the maximum rms power the amplifier can deliver into the 8.0 ohm load before

signal clipping occurs? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) What input voltage would be required to drive the amplifier to maximum output? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 25 A capacitor (0.10 µF), an inductor (0.13 H) and a 12 ohm resistor are connected in series. (a) Sketch a diagram illustrating this configuration. (1 mark) (b) (i) Calculate the resonant frequency of the network. (3 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Determine the impedance of the network at the resonant frequency. (1 mark) .................................................................................................................................... .................................................................................................................................... (c) Sketch a graph of impedance ~ frequency for this network. (1 mark)

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Question 26

(a) Calculate the value of C that will make the rms voltage across C equal to the rms voltage across the 1k resistor, at the given frequency. (2 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) (i) What is the rms voltage across each component at 1 kHz, with the value of C from

part (a)? (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Why does the sum of these rms voltages not equal the input voltage? (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

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1 k

C

Input

10 V rms

1 kHz


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Question 27 Consider this resistor array.

(a) Show that the resistance of the parallel combination is approximately 330 Ω. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) If the voltage at X, VX, is to be 8.0 V, calculate the nearest E12 value required for R1. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 28 A digital logical circuit is given by:

(a) Write a Boolean expression for this circuit. (1 mark) ............................................................................................................................................. ............................................................................................................................................. (b) Complete the truth table for the circuit. (2 marks)

A B W X Y Z 0 0 0 1 1 0 1 1

(c) Describe the operation of the circuit. (1 mark) ............................................................................................................................................. .............................................................................................................................................

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X

Z

Y

W

A

B


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Question 29 A green LED has the following specifications: A green LED is to be used as an indicator and is connected to a 15 V supply. (a) What will the voltage drop across the LED be when it is glowing? (1 mark) ............................................................................................................................................. (b) What is the maximum current that should be permitted to flow through the LED? (1 mark) ............................................................................................................................................. (c) Calculate the minimum E12 value of the required dropper resistor. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) Find the power dissipated in this dropper resistor. (1 mark) ............................................................................................................................................. .............................................................................................................................................

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Type Nominal Size

(mm)

Lens FWD Voltage

Max Cont

Forward Current (mA)

Max Rev Voltage

Luminous Intensity

(mcd)

@ current (mA)

Peak Wavelength

(nm)

Green 5 dia Green diffused 2.3 15 5 3 10 525


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Question 30 Below is a flowchart for a PICAXE program designed to test an LDR. The ‘readadc’ command is used to read the analogue value (a number between 0 and 255) into variable b1. Once the number is in variable b1, it can be tested to see if it is greater than 100 or greater than 50. If the number:

• is greater than 100, then output 4 is switched on • is between 50 and 100, output 0 is switched on • is less than 50, then both outputs are switched off. Use this flowchart to write an annotated BASIC program designed to control the Picaxe. (7 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... .......................................................................................................................................................


b1> 100

start

readadc 1,b1

b1> 50

low 0

low 4

high 0

low 4 low 0

high 4


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Page 26

SPARE DIAGRAMS

Question 16 (c)

Question 19 (b) Question 22 (b)

Speaker Filter Tweeter

(High frequency)

Mid-range Woofer

(Low frequency)


Page 27

SPARE DIAGRAMS

Question 25 (c)

Question 28 (b)

A B W X Y Z 0 0 0 1 1 0 1 1


Page 28

This question paper and any materials associated with this examination (including answer booklets, cover sheets, rough note paper, or information sheets) remain the property of the Tasmanian Qualifications Authority.

Electronics


2014 External Examination Information Sheet

Page 1 of 3

Frequency, period

€

f =1T

Ohm’s Law

€

V = IR,

€

I =VR

, R =VI

Power

€

P =VI , P = I2R, P =V 2

R

Current

€

I =PV

, I =PR

Voltage

€

V = PR

€

V =PI

Resistance

€

R =PI2 , R =

V 2

P

Resistors in series RT = R1 + R2 + R3 + ....

Resistors in parallel 1RT

=1R1

+1R2

+1R3

+ ....

or

€

RT = R1−1 + R2

−1 + R3−1 + ...( )

−1

Capacitors in series 1CT

=1C1

+1C2

+1C3

+ ....

or

€

CT = C1−1 + C2

−1 + C3−1 + ...( )

−1

Capacitors in parallel CT = C1 + C2 + C3 + ....

Inductive reactance XL = 2π f L

Capacitive reactance XC =1

2π f C

RC filter cut off frequency fc =1

2π RC

Impedance ZT = 2R + 2X , X = XL − XC

LC filter resonance

€

f =1

2π LC, C =

1L

. 12πf#

$ %

&

' (

2, L =

1C

. 12πf#

$ %

&

' (

2

RC time constant T RC=

RL time constant TLR

=

Page 2 of 3

Gain

negative gain for an inverting amplifier

€

G =−VoutVin

or

€

−G = RfRin

for a non-inverting amplifier

€

G =VoutVin

or

€

G = 1+RfRin

or

€

G =Rf + RinRin

Summing Amplifier Gain

€

–VoutR f

=Vin1Rin1

+Vin2Rin2

+Vin3Rin3

or

€

Vout = –RfV1R1

+V2R2

+V3R3

"

# $

%

& '

Power Gain(dB)

€

G =10log PoutPin

or

€

20 log Vout

Vinprovided Zin = Zload( )

Peak voltage

€

Vpeak =1.414VRMS RMS voltage

€

VRMS = 0.707Vpeak

Voltage divider

€

Vout =R2

R1 + R2. Vin

Resistor colour code Capacitor value code

Colour digit multiplier tolerance Silver x 0.01 ±10% Gold x 0.1 ±5% Black 0 x 1 Brown 1 x 10 ±1% Red 2 x 100 ±2% Orange 3 x 1000 ±3% Yellow 4 x 10000 ±4% Green 5 x 100000 ±0.5% Blue 6 x 1000000 ±0.25% Violet 7 Grey 8 White 9

First two numerals represent first two digits of capacitor’s value, in picofarads Third numeral represents multiplier (power of 10) e.g. 1000 pF has code 102 10 nF = 10,000 pF has code 103 2.2µF = 2,200,000 pF has code 225

E12 Values 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 Logic gates

AND

OR

XOR

NAND

NOR

XNOR

NOT

Clock Inputs PGE NGE

Page 3 of 3

Passive Filters Low Pass High Pass Band Pass Band Stop (Notch) RC

RL

LC

Active Filters

Only one input or feedback filter required, but will work with both. Input or feedback filter is passive filter as above.

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ELT315114 Part 1 - Department of Education · · 2017-07-21electronic circuit. (2 marks) ... (2 marks) Question 10 continues. Electronics – Part 1 Page 15 ... likely behaviour