Cambridge IGCSE Design and Technology 0445 — 2022 Oct/Nov Paper 4 · Variant 3

1 Fig. 1.1 shows two methods of packaging drinks. plastic glass bottle bottle Fig. 1.1 (a) Give one environmental reason for using glass bottles. ............................................................................................................................................. [1] (b) Give one functional reason for using plastic bottles. ............................................................................................................................................. [1] (c) Name the type of structure used in both bottles in Fig. 1.1. ............................................................................................................................................. [1]

Mark scheme: Question Answer Marks Guidance 1(a) Reasons for using glass will include: 1 Allow any other valid reason. • Easy recycling • Hygienic, can be used multiple times • The raw materials used are not based on fossil fuels • Reusable • Less pollution caused. 1(b) Functional reasons for plastics will include: 1 Do not allow unjustified reasons related to • Lighter to transport / lightweight cost. • Easily resealable Allow any other valid reason. • Plastic bottles do not break easily / more durable • Handles can easily be moulded into the shape • Suitable for bulk manufacture. 1(c) Both bottles are a shell structure, 1 mark. 1

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2 Fig. 2.1 shows a skeleton leaf. Fig. 2.1 State the type of structure that forms the leaf. .................................................................................................................................................... [1]

Mark scheme: 2 The skeleton leaf is a frame structure, 1 mark 1

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3 Most electricity pylons are made from steel. Give three reasons why steel is a suitable material for the manufacture of electricity pylons. 1 ....................................................................................................................................................... .......................................................................................................................................................... 2 ....................................................................................................................................................... .......................................................................................................................................................... 3 ....................................................................................................................................................... .......................................................................................................................................................... [3]

Mark scheme: 3 Reasons for steel being suitable for pylons include: 3 Allow other valid reasons. • Relatively low cost Do not allow reference to resisting • Plentiful supply corrosion. • Can be recycled. • Strong in tension • Strong in compression • Resists torsion / bending • Steel is a durable material • Can be produced in several suitable sections, e.g. angle section. • Easily joined by mechanical means or heat processes. 3  1 marks

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4 Use sketches to show an example of: • a first order lever • a third order lever. first order lever third order lever [2]

Mark scheme: 4 • First order lever, 1 mark 2 Drawing must be above the correct heading • Third order lever, 1 mark unless a separate heading has been used.

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5 Give three reasons for choosing to use spur gears to transmit motion in a mechanism. 1 ....................................................................................................................................................... .......................................................................................................................................................... 2 ....................................................................................................................................................... .......................................................................................................................................................... 3 ....................................................................................................................................................... .......................................................................................................................................................... [3]

Mark scheme: 5 Reasons for using spur gears include: 3 Allow other valid reasons. • To connect two shafts together / transmitting rotary motion • The gears will not slip • Gear ratio is easily changed • Transfer / increase torque effectively • Can be easily reversed by using an idler gear • Low cost materials can be used, e.g. nylon. 3  1 marks

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6 Fig. 6.1 shows a method of providing lubrication to a mechanism. oil Fig. 6.1 (a) Give two benefits of providing lubrication by the method shown in Fig. 6.1. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2] (b) Explain why lubrication is important in a mechanism with moving parts. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2]

Mark scheme: 6(a) Benefits include: 2 To gain marks the response must refer to • Visible reference to level of oil remaining the method of lubrication. • Gravity fed, does not rely on a pump • More efficient than hand lubrication • Low maintenance system • Regular feed of oil to the mechanism. • No spilled oil on surrounding parts 2  1 marks 6(b) Explanation should include the following points: 2 One mark for each point mentioned. • Reduced friction / efficiency is increased Allow two marks for a single point fully • Lubrication will prevent wear / corrosion in the mechanism components explained. • Mechanism is kept cool Allow reference to smooth running. • Reduced noise from the mechanism • Dirt or debris is carried away from the moving parts • Build-up of heat due to friction is reduced.

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7 Complete table 7.1 to give an alternative format for showing each electrical measurement. Table 7.1 Electrical Alternative measurement format 0.097 V mV 1500 pF nF 0.001 A mA 36 000 000 Ω MΩ [4]

Mark scheme: 7 4 Electrical Alternative format measurement 0.097 V 97 mV 1500 pF 1.5 nF 0.001 A 1 mA 36 000 000  36 M 4  1 marks.

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8 Fig. 8.1 shows a microswitch. NC C NO Fig. 8.1 (a) Draw the circuit symbol for the microswitch. [1] (b) Describe how the microswitch works. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2]

Mark scheme: 8(a) 1 Accept any other recognisable version of a SPDT switch symbol. 8(b) • The microswitch is operated by pressure on the lever actuating switch 2 No mark for general statements • The pressure needed is very light e.g. allows electricity to flow. • The Common is connected to Normally Closed when not pressed • When pressed Common is connected to Normally Open. Description to include any 2 of the above points.

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9 Describe the difference between a PTM switch and a PTB switch. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [2]

Mark scheme: 9 The contacts on a PTM switch will close when the switch is operated 2 The contacts on a PTB switch will open when the switch is operated. Section B

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10 Fig. 10.1 shows an archery bow. ................................................. ................................................. ................................................. Fig. 10.1 (a) (i) Label the area of the bow that is: • in compression • in tension • the neutral axis. [3] (ii) Give two benefits of using composite laminated materials, rather than a single piece of wood, to make a bow. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... [2] (iii) Give one property of an adhesive needed when joining the materials in a composite laminated bow. ........................................................................................................................................... ..................................................................................................................................... [1] (iv) Name two composites and the materials that are used in their manufacture. Name of composite 1 ........................................................................................................ Materials used in manufacture .......................................................................................... Name of composite 2 ........................................................................................................ Materials used in manufacture .......................................................................................... [6] (b) Fig. 10.2a shows a structure used in a multi-storey building to support window openings. The structure includes ties and struts. steel tube steel tube steel rods Fig. 10.2a Fig. 10.2b (i) Add labels for a tie and a strut on Fig. 10.2b. [2] (ii) Ties are often made adjustable in length. Use sketches and notes to show one way of making a tie adjustable in length. [3] (c) (i) Fig. 10.3 shows two steel beams of equal length. A B Fig. 10.3 Explain why beam A can withstand more load than beam B without bending in the centre. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Calculate the reactions R1 and R2 when beam A is loaded as shown in Fig. 10.4. 5.2 m 1.8 m 2 m 1200 N 1200 N R1 R2 Fig. 10.4 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [4] (iii) Describe how Factor of Safety contributes to the design of a structure that uses beams. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2]

Mark scheme: 10(a)(i) 3 1 mark for each correct label. 10(a)(ii) Benefits of composites will include: 2 Allow any other valid benefits, e.g. • Material is more stable reference to ‘aesthetic qualities’, ‘increased • Natural defects in the materials can be avoided strength’. • Greater range of designs are possible • Increased durability of the composite 10(a)(iii) Adhesive properties will include: 1 Allow other valid properties. • Flexibility will be needed • Moisture resistance / waterproof • Unaffected by change in temperature • Resistant to applied forces e.g. shear / tension • ‘Gap filling’ qualities. 1 mark 10(a)(iv) Examples of composites include: 6 Allow other composites such as Kevlar and Resin based, ceramic composites. GRP – polyester resin and glass fibres Allow Fibreglass for GRP Carbon fibre – graphite fibres bonded with resin Concrete – Portland cement and aggregate Reinforced concrete – Concrete with the addition of reinforcing bars that are strong in tension 1 mark for names 2  1 2  2 marks for constituent materials. 10(b)(i) 2 1 mark for each correct label, 2  1 marks 10(b)(ii) Change in length provided, 1 mark e.g. left and right hand threads on a 3 connector. Adjustable method, capable of being tightened and loosened 1 mark Clear sketches / notes, 1 mark 10(c)(i) The following points could be included: 2 One mark for each point mentioned. • Increased depth of the web will resist bending on beam A. Allow two marks for a single point fully • The top and bottom flanges are supporting the central web explained. • In beam B there is less depth to resist the bending caused by a load on the beam. 10(c)(ii) Taking moments about R1 4 Award full marks for correct answer with no (1.8  1200) + (3.8  1200) = R2  5.2, 1 mark working. 2160 + 4560 = R2  5.2, 1 mark 6720 / 5.2 = R2 = 1292.3 N, 1 mark The reaction at R1 is 2400 – 1292.3 = 1107.7 N, 1 mark 10(c)(iii) • The factor of safety of a structural design will be calculated from the 2 One mark for each point mentioned. failure loading divided by a number, the factor of safety. Allow two marks for a single point fully • This means that even under exceptional conditions the structure should explained. not fail. • A higher factor of safety number will result in the design load that the structure can take being lower. • Accurate calculation and use of the factor of safety means that there is reduced chance of the structure collapsing.

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11 Fig. 11.1 shows a bolt with a screw thread cut into it. 54 1.75 9.85 12.00 0.87 Fig. 11.1 (a) (i) State the conversion of motion that takes place when using a screw thread. ................................................................ to ................................................................ [1] (ii) Screw threads are made in standard sizes. Give two benefits of using standard sizes of thread. 1 ........................................................................................................................................ 2 ........................................................................................................................................ [2] (iii) State which two dimensions in Fig. 11.1 form part of the standard size for the thread. 1 ........................................................................................................................................ 2 ........................................................................................................................................ [2] (b) Fig. 11.2 shows two types of clothes peg used to secure clothes to a washing line. Both types of clothes peg use leverage when in use. soft plastic wood hard plastic A B Fig. 11.2 (i) Mark the position of the fulcrum on peg A. [1] (ii) Describe the difference in operation of the springs in each clothes peg. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (iii) Explain why peg A is considered a more sustainable product than peg B. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (c) Fig. 11.3 shows a derailleur gear mechanism on a bicycle. 28 t sprocket jockey wheels Fig. 11.3 (i) Describe the purpose of the derailleur gear mechanism. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) The jockey wheels use sealed ball bearings to allow free rotation. Give two reasons why this method has been chosen rather than individual ball bearings. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... [2] (iii) The chainwheel that drives the bicycle has 49 teeth. Calculate the Velocity Ratio when the chain is on the 28-tooth rear sprocket as shown in Fig. 11.4. 28 t rear sprocket 49 t chainwheel Fig. 11.4 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (iv) Calculate the speed of the rear wheel if the chainwheel is rotating at 78 rpm. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (v) Explain why the drive system will not be 100% efficient. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (d) Fig. 11.5 shows a linkage used to operate railway signals. A B grease points fixed pivots Fig. 11.5 (i) Give two reasons why grease has been used to lubricate the moving parts of the linkage rather than oil. 1 ........................................................................................................................................ 2 ........................................................................................................................................ [2] (ii) Describe the effect on the linkage of moving rod A in the direction of the arrow. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2]

Mark scheme: 11(a)(i) Rotary to Linear, 1 mark. 1 11(a)(ii) Benefits will include: 2 Allow other valid benefits. • Reduced stock • Interchangeability of components • Helps global manufacturing • Easier to get spare / replacement parts. 2  1 marks 11(a)(iii) The thread diameter 12.00 mm (M12), 1 mark 2 The thread pitch 1.75mm, 1 mark. 11(b)(i) 1 Correctly marked fulcrum position, 1 mark. 11(b)(ii) In peg A the spring is under torsion when the peg is opened, 1 mark 2 For peg A allow tension. In peg B the spring is compressed when the peg is opened, 1 mark. 11(b)(iii) Points will include: 2 Allow other valid points. • The wooden parts of the peg have come from a sustainable resource 1 mark for each valid point mentioned in • The two types of plastic bonded together in peg B prevents recycling explanation. • The plastic comes from a non-renewable resource. Allow 2 marks for single point fully explained. 11(c)(i) The purpose of the mechanism is: 2 Allow 1 mark for the benefits of using a • To move the chain from one sprocket to another lower gear. • To keep the chain in tension. 2  1 marks 11(c)(ii) • Individual bearings make maintenance more difficult 2 • A sealed bearing will not allow water or grit to enter • To prevent individual bearings falling out during maintenance • The jockey wheel will last longer. 2  1 marks 11(c)(iii) Velocity ratio = driver gear / driven gear, 1 mark 2 Allow 7:4 49 / 28 = 1.75, 1 mark 11(c)(iv) Rear wheel speed = chainwheel speed  VR, 1 mark 2 Award both marks for correct answer with 78  1.75 = 136.5 rpm, 1 mark no working. Allow ecf. 11(c)(v) The efficiency of the drive system will be reduced by: 3 One mark for each point mentioned. • Friction in all the moving parts Allow two marks for a single point fully • Sound created by the drive system, explained. • Heat generated by the moving parts • Lack of lubrication of moving part 11(d)(i) Reasons for using grease include: 2 Reasons given must compare the use of • Oil could drain away from the lubrication point grease to the use of oil. • Rain / snow could quickly wash oil away • Excessive heat in the summer would dry the oil up • Reduced chance of grit gaining access to the pivots. 2  1 marks. 11(d)(ii) If rod A is moved to the left: 2 One mark each for any two points • The LH bell crank will rotate anti-clockwise about the fixed pivot. mentioned. • The central link is then pushed to the right. • The RH bell crank rotates clockwise about the fixed pivot. • Rod B moves to the right, in the opposite direction to rod A

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12 (a) Fig. 12.1 shows four logic gate symbols. (i) Name each symbol on Fig. 12.1. ........................... ........................... ........................... ........................... Fig. 12.1 [4] (ii) Describe what a NOT gate is. ..................................................................................................................................... [1] (iii) Draw a NOT gate made from one of the gates in Fig. 12.1. [2] (iv) The output signal from a logic gate can only provide a very low current. Fig. 12.2 shows a method of amplifying the output current in the output signal from a logic circuit. 5 V R2 output signal from logic circuit R1 X Y 0 V Fig. 12.2 State the purpose of components R1, R2, X and Y in the circuit. R1 ...................................................................................................................................... R2 ...................................................................................................................................... X ........................................................................................................................................ Y ........................................................................................................................................ [4] (b) Fig. 12.3 shows part of a circuit for a light operated switch which will give a high output in the dark. The circuit uses an operational amplifier to compare voltages at X and Y. +9 V LDR 1 10 kΩ – X Y + VR1 VR2 V 4.6 V V 6.5 V 0 V Fig. 12.3 (i) On Fig. 12.3 make the following connections: • point X to the inverting input of the op-amp • point Y to the non-inverting input of the op-amp. [2] (ii) Describe what happens to LDR1 and the voltage at point X when the light level falls. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (iii) Calculate the resistance setting of VR2 for the output voltage shown. R2 Use the formula Vout = Vin × R1 + R2 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [4] (c) Fig. 12.4 shows the outline of the comparator IC. Fig. 12.4 (i) Add the pin numbers to the outline of the IC. [2] (ii) Fig. 12.5 shows the solder side of a printed circuit board with an IC holder ready to be soldered in place. Fig. 12.5 Give the reason for two of the pins being bent over. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) State two health and safety procedures that should be used when soldering components to a circuit board. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... [2]

Mark scheme: 12(a)(i) AND, NAND, OR, NOR, 1 mark for each 4 12(a)(ii) A NOT gate or inverter will change a logic signal level to the opposite level, 1 Award mark for understanding shown. logic 1 becomes logic 0 and logic 0 becomes logic 1 12(a)(iii) 2 Accept either NAND or NOR gate as a NOT gate. Correct gate used, 1 mark Inputs connected, 1 mark 12(a)(iv) R1 is a current limiting resistor to protect the transistor. 4 Award marks for understanding shown. R2 is a pull up resistor to provide a logic 1 signal when 0 is input from the logic circuit. X is a NOT gate which inverts the input signal allowing the output signal to be at the same logic level as the input. Y is an NPN transistor to amplify the current from the input signal. 12(b)(i) 2 - X Y + 1 mark for each correct connection. 12(b)(ii) The resistance of LDR1 will change, 1 mark 3 The resistance increases 1 mark as light level decreases, 1 mark The voltage at X will decrease, 1 mark. 3 x 1 marks 12(b)(iii) 6.5 = 9  VR2 / (10 k + VR2) 6.5 / 9 = VR2 / (10 k + VR2), 1 mark 4 Award 4 marks for correct answer with no 0.722  (10 k + VR2) = VR2, 1 mark working. 7.22 + (0.722  VR2) = VR2, 1 mark 7.22 = 0 .278 VR2 VR2 = 7.22 / 0.278 = 25.97 kΩ, 1 mark Allow use of alternative formula or ohms law Vtotal = 9 V, V1 = 2.5 V, V2 = 6.5 V or V 1 R1 = x = R 2 6.5 = 9  VR2 / 10+VR2 1 mark V 2 x 6.5  (10+VR2) = 9  VR2 1 mark 65 + 6.5 VR2 = 9 VR2 1 mark 2.5 / 6.5 = 0.3846 65 = 9 VR2 – 6.5 VR2 = 2.5 VR2 VR2 = 65 / 2.5 = 26 kΩ 1 mark 10 k / 0.3846 = R2 = 26 k 12(c)(i) 1 8 2 2 7 [1] 3 6 [1] 4 5 Pins 1–4 correct, 1 mark. Pins 5–8 correct, 1 mark. 12(c)(ii) The pins are bent over to secure the IC / IC holder while it is being soldered. 1 12(c)(iii) Health and Safety procedures while soldering will include: 2 Allow any other valid procedures that should • Safety glasses be carried out. • Fume extraction • Checking the soldering iron cable for damage • Fixing circuit board so that it does not move about • Washing hands after handling lead based solder. 2  1 marks.

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