2025 CCEA GCSE Technology and Design 8900 模拟试题及答案详解

Any two valid PPE items may be given. Safety goggles (or safety glasses) protect the eyes from flying swarf, and an apron or overall-style apron protects clothing and helps prevent loose clothing becoming entangled in the rotating chuck. Final answer: safety goggles and an apron.

[1] mark for each valid PPE item named, to a maximum of 2 marks. Accept: safety goggles/glasses; apron/overall. Reject general safe-working practices that are not items of PPE (e.g. 'tie back hair').

Visible outlines are drawn using a continuous thick line. Hidden edges or features that cannot be seen from the current viewpoint are drawn using a dashed (short-dash) line. Final answer: (a) continuous thick line; (b) dashed line.

[1] continuous/thick line for a visible outline; [1] dashed/hidden-detail line for a hidden edge.

Ferrous metals contain iron, for example mild steel or cast iron. Non-ferrous metals contain no iron, for example aluminium, copper or tin. Final answer: mild steel (ferrous) and aluminium (non-ferrous).

[1] correct ferrous metal named (e.g. mild steel, cast iron, high carbon steel); [1] correct non-ferrous metal named (e.g. aluminium, copper, tin, zinc).

Thermoplastics are made of polymer chains held together by weak intermolecular forces, so heating allows the chains to slide past one another and the material softens and can be remoulded repeatedly. Thermosetting polymers have strong covalent cross-links formed permanently between chains during manufacture, so heating does not soften them; instead they char or burn. Final answer: thermoplastics soften/can be reshaped on heating, whereas thermosets do not soften and char instead.

[1] correct statement about thermoplastic behaviour on heating (softens/can be reshaped or remoulded); [1] correct statement about thermoset behaviour on heating (does not soften/chars/cannot be remoulded).

A try square (or engineer's square) has a stock and a blade fixed at exactly 90 degrees, so when the stock is held against a true edge, the blade can be used to scribe an accurate right angle onto the surface. Final answer: try square.

[2] for a correct tool capable of marking an accurate 90° angle against a true edge (try square/engineer's square/combination square); [1] for a tool that can only mark a straight line but not verify a right angle (e.g. a ruler/steel rule).

A hand plane, such as a smoothing plane or jack plane, removes thin shavings of waste wood from a face or edge using a sharpened blade, producing a smooth, flat surface. This is a cutting (wasting) process, distinct from sanding, which removes material using abrasive particles rather than a blade. Final answer: planing.

[2] for planing/use of a hand plane; accept chiselling, filing or spokeshaving of wood as alternative wasting processes for [2]; [1] for a vaguer but still valid wasting term without a correctly named tool/process.

Permanent joining methods for mild steel sheet include welding (e.g. MIG welding, which locally melts and fuses the two pieces together), brazing, or riveting, none of which can be separated again without damaging the parts. Final answer: welding.

[2] for a valid permanent joining method (welding/brazing/riveting/soldering of metal); [1] if a semi-permanent method is given instead (e.g. self-tapping screw) — award the method mark only, not the 'permanent' mark.

Brown = 1 and black = 0, giving the significant digits 10. Red is the multiplier band, meaning ×100. So the resistance is 10 × 100 = 1000 Ω = 1 kΩ. Gold is the tolerance band, meaning ±5%. Final answer: 1 kΩ ± 5%.

[1] correct resistance value (1000 Ω / 1 kΩ); [1] correct tolerance (±5%).

An LED only emits light when it is forward biased, i.e. connected so that current flows from anode to cathode once the voltage across it exceeds its forward threshold voltage (typically around 2 V for a standard LED). Because an LED has very low resistance once forward biased, a series resistor is needed to limit the current flowing through it and prevent the LED from being damaged by excess current. Final answer: forward biased; the series resistor limits/protects against excess current.

[1] LED must be forward biased (connected the correct way round, with voltage exceeding its threshold); [1] resistor limits current to protect the LED from damage.

A bevel gear has teeth cut onto a conical surface, allowing it to mesh with a matching bevel gear so that rotary motion is transmitted through a 90° change in the axis of rotation. Final answer: bevel gear.

[2] for bevel gear (mitre gear accepted as a special case); [1] for worm gear, which also changes the axis by 90° but is primarily used for large speed reduction rather than simple right-angle drive.

The numbers used to designate a pneumatic valve refer to the number of ports (connections) and the number of positions the valve can be switched between. A 5/2 valve therefore has 5 ports and 2 positions, and is commonly used to control a double-acting cylinder. Final answer: 5 ports, 2 positions.

[1] '5' = number of ports; [1] '2' = number of switching positions.

In a single-acting cylinder, compressed air is supplied to only one port, powering the piston in one direction only (usually extending it). There is no air supply to move the piston back, so a spring built into the cylinder returns the piston to its start position once the air supply to it is released/exhausted. Final answer: air moves the piston one way only; a spring returns it.

[1] air/pressure acts on one side of the piston only (a one-directional power stroke); [1] correct return mechanism identified (spring return, not air).

Standard flowchart symbols: a decision point, where the process branches depending on the answer to a yes/no question, is drawn as a diamond (rhombus). An input or output step, such as reading a sensor value or displaying a result, is drawn as a parallelogram. Final answer: (a) diamond; (b) parallelogram.

[1] diamond/rhombus for a decision; [1] parallelogram for an input/output.

A CAM machine, such as a CNC router or laser cutter, follows the same digital toolpath every time it runs, so every component produced is essentially identical and highly accurate, removing the variation in accuracy caused by operator skill or fatigue that occurs when machining manually. Final answer: greater accuracy and consistency/repeatability between identical parts.

[2] for a valid advantage clearly explained (e.g. improved accuracy/repeatability/consistency between parts; faster production once set up; reduced operator skill required); [1] for a valid advantage stated only as an unexplained single word/phrase.

Cast iron contains iron, so it is a ferrous metal. Copper is a metal containing no iron, so it is non-ferrous. Acrylic (PMMA) and HDPE are both synthetic polymers (thermoplastics). Carbon fibre reinforced plastic combines a polymer resin with carbon fibre reinforcement, making it a composite material. Final answer: Cast iron - ferrous; Copper - non-ferrous; Acrylic - polymer; CFRP - composite; HDPE - polymer.

[1] mark per correctly classified material, to a maximum of 5: Cast iron = ferrous metal; Copper = non-ferrous metal; Acrylic (PMMA) = polymer; Carbon fibre reinforced plastic = composite; HDPE = polymer.

Turning and drilling both remove material from a workpiece using a cutting edge, so both are wasting processes. Vacuum forming and line bending (strip heating) both change the shape of a sheet material by heating and moulding/bending it without removing material, so both are forming processes. Riveting permanently fixes two components together, so it is a joining process. Final answer: Turning - wasting; Vacuum forming - forming; Drilling - wasting; Riveting - joining; Line bending - forming.

[1] mark per correct classification, to a maximum of 5, as listed in the solution.

Welding fuses materials together and cannot be undone without damage, so it is permanent, as is a correctly applied structural epoxy adhesive bond. A nut and bolt can be removed and reused repeatedly with a spanner, so it is temporary, as is a toggle/spring clip designed for quick release. A self-tapping screw can be removed and replaced only a limited number of times before the thread it cuts is damaged, so it is classed as semi-permanent. Final answer: Welding - permanent; Nut and bolt - temporary; Adhesive - permanent; Self-tapping screw - semi-permanent; Toggle/spring clip - temporary.

[1] mark per correct classification, to a maximum of 5, as listed in the solution.

A rack and pinion converts the rotary motion of the pinion into linear motion of the rack. A bevel gear pair transmits rotary motion between two shafts, changing its axis but remaining rotary to rotary. In an engine, the crank and slider mechanism converts the reciprocating (back-and-forth) motion of the piston into rotary motion of the crankshaft. A cam and follower converts the rotary motion of the cam into linear (reciprocating) motion of the follower. A pulley and belt drive transmits rotary motion from one shaft to another, so it remains rotary to rotary. Final answer as listed above.

[1] mark per correctly identified motion conversion, to a maximum of 5, as listed in the solution. Accept 'rotary to reciprocating' as equivalent to 'rotary to linear' for the cam and follower.

Actuators are the components that do the physical work in the system - both the double-acting and single-acting cylinders are actuators, converting air pressure into linear movement. A 5/2 solenoid valve is a control (directional) valve, switching the main air supply to the actuator. A 3/2 roller-trip valve and a manual push-button valve are signal elements - they are actuated by a mechanical trip or by an operator to send a pilot signal into the circuit, rather than powering the actuator directly. Final answer as listed above.

[1] mark per correct classification, to a maximum of 5, as listed in the solution.

(a) In isometric sketching, the two sets of receding lines that represent the horizontal edges of the object are drawn at 30 degrees to the horizontal. (b) Vertical edges of the object remain drawn as vertical lines in the sketch. (c) Isometric sketching preserves true length along all three isometric axes (unlike true isometric projection, which foreshortens each axis), so a 20 mm edge is drawn 20 mm long. (d) Because an isometric sketch shows three faces of the object in a single 3D view, it is easier for someone without technical drawing knowledge, such as a client, to understand the overall form of the design than from a set of separate 2D orthographic views. Final answer: (a) 30 degrees; (b) vertical; (c) 20 mm; (d) easier 3D visualisation for a non-technical audience.

[1] 30 degrees; [1] drawn as vertical lines; [1] 20 mm (accept 'the same as the true length'); [1] valid advantage relating to 3D visualisation/communicating with a client.

Using the potential divider formula: \( V_{out} = V_{in} \times \dfrac{R_2}{R_1+R_2} \). Substituting the given values: \( V_{out} = 8 \times \dfrac{600}{200+600} = 8 \times \dfrac{600}{800} = 8 \times 0.75 \). This gives \( V_{out} = 6\text{ V} \). Final answer: Vout = 6 V.

[1] correct formula stated \( V_{out} = V_{in} \times \frac{R_2}{R_1+R_2} \); [1] correct substitution of given values; [1] correct working/simplification; [1] final answer 6 V with correct unit. Error carried forward applies if a substitution slip is carried through consistently.

Velocity ratio \( VR = \dfrac{\text{teeth on driven gear}}{\text{teeth on driver gear}} = \dfrac{54}{18} = 3 \). Output (driven gear) speed \( = \dfrac{\text{input speed}}{VR} = \dfrac{300}{3} = 100 \) rpm. Final answer: the driven gear rotates at 100 rpm, in the opposite direction to the driver since this is a simple two-gear mesh.

[1] correct velocity ratio calculated (VR = 3); [1] correct method/substitution to find the output speed; [1] final answer 100 rpm. Error carried forward applies if VR is carried forward incorrectly but the method is otherwise sound.

(i) Pressing the push-button switches the 3/2 valve to its other position, connecting the compressed air supply to the cylinder port, so the piston extends. (ii) Releasing the button allows the valve's internal spring to switch it back, connecting the cylinder port to exhaust instead of the supply, so no supply pressure reaches the piston. (iii) With no air pressure acting on it, the cylinder's own internal return spring pushes the piston back to its retracted start position. Final answer: (i) piston extends; (ii) supply cut off/exhausted; (iii) spring returns the piston to start.

[1] piston extends on pressing the button (air supplied); [1] air supply cut off/exhausted on release; [1] spring returns the piston to its start position.

A correctly sequenced flowchart for this system is as follows. 1) START (terminator symbol). 2) INPUT: read the moisture sensor value (parallelogram). 3) DECISION: is the moisture level below the threshold? (diamond, with YES and NO branches). 4) YES branch: PROCESS - switch the pump ON (rectangle); then DELAY - wait 5 seconds (rectangle, delay/timer operation); then PROCESS - switch the pump OFF (rectangle); then DELAY - wait 10 minutes (rectangle, delay/timer operation); the flow then loops back (feedback line) to step 2, read the moisture sensor value again. 5) NO branch: DELAY - wait 10 minutes; the flow then also loops back (feedback line) to step 2. There is no END terminator, since the system repeats continuously. Final answer: START -> read sensor (input) -> decision (moisture < threshold?) -> YES: pump ON -> wait 5 s -> pump OFF -> wait 10 min -> loop to read sensor; NO: wait 10 min -> loop to read sensor.

[1] START terminator correctly placed at the beginning; [1] INPUT operation to read the moisture sensor, shown as a parallelogram; [1] DECISION box correctly testing moisture against the threshold, shown as a diamond; [1] correctly labelled YES branch; [1] correctly labelled NO branch; [1] PROCESS: pump switched ON on the YES branch; [1] DELAY: wait/timer of 5 seconds after pump ON; [1] PROCESS: pump switched OFF after the delay; [1] DELAY: wait/timer of 10 minutes shown on the YES branch (after pump OFF); [1] DELAY: wait/timer of 10 minutes shown directly on the NO branch; [1] feedback loop correctly returning the YES branch to the input/read-sensor step; [1] feedback loop correctly returning the NO branch to the input/read-sensor step (continuous cycle, no END terminator required). Maximum 12 marks.

The output voltage of the potential divider is taken across the LDR: \( V_{out} = V_{in} \times \dfrac{R_{LDR}}{R_{fixed}+R_{LDR}} \). As light levels fall, the resistance of the LDR, \(R_{LDR}\), increases. Because \(R_{LDR}\) is in the numerator of this formula, an increase in \(R_{LDR}\) increases \(V_{out}\). Once \(V_{out}\) rises above the transistor's base-emitter threshold voltage (approximately 0.7 V for a silicon NPN transistor), the transistor switches from off to on, allowing current to flow from collector to emitter and lighting the LED. Final answer: darkness increases the LDR's resistance, which increases the base voltage until it exceeds the transistor's threshold, switching the transistor and LED on.

[1] LDR resistance increases as it gets darker; [1] this increases Vout/the voltage across the LDR, correctly linked to the potential divider formula/reasoning; [1] once Vout exceeds the transistor's threshold voltage (approximately 0.7 V) the transistor switches on, lighting the LED.

A flow control valve contains an adjustable restrictor, often combined with a one-way non-return valve to allow full-speed flow in one direction. When fitted to the exhaust port, it restricts (throttles) how quickly air already in the cylinder can escape as the piston moves; the more the valve is closed, the more restricted the exhaust flow, so the more slowly the piston moves, since its speed is limited by how fast the air ahead of it can leave. Final answer: restricting the exhaust air flow slows the piston's speed.

[1] the valve restricts/throttles the exhaust air flow; [1] this is correctly linked to a reduced/controlled piston speed.

A jig is a work-holding device that positions the workpiece and guides the cutting tool, for example via a hardened drill bushing, to a pre-set location. Using a jig for a batch of components means every hole is positioned identically without needing to mark out and align each component individually, which increases the accuracy and consistency between parts and also speeds up production. Final answer: a jig ensures holes are positioned accurately and consistently in the same place on every component in the batch.

[1] the jig locates/holds the workpiece and guides the tool; [1] this is correctly linked to improved accuracy/consistency, or speed, across the batch.

A rivet requires a hole to be drilled through both materials, which concentrates stress at that point and risks cracking a brittle polymer panel; a single-point metal fixing can also work loose over time as dissimilar materials expand and contract at different rates. An adhesive bond instead spreads the joining force evenly over the whole contact area, requires no holes, and can accommodate small differences in movement between the two dissimilar materials while also sealing the joint against moisture. Final answer: adhesive spreads the load over the full area and avoids drilling, reducing the risk of cracking a brittle or dissimilar material.

[1] adhesive spreads the load over the whole bonded area rather than a single point, and avoids drilling holes; [1] this is correctly linked to a benefit for dissimilar materials (e.g. avoids cracking a brittle material, accommodates differential expansion, or seals against moisture).

Adding a third (idler) gear between the driver and the driven gear means the driven gear now rotates in the same direction as the driver, since each mesh reverses direction and there are now two meshes instead of one; it also allows the driver and driven gears to be positioned further apart. Because the idler gear's own tooth count appears once in the numerator and once in the denominator of the overall gear ratio calculation, it cancels out and does not change the overall velocity ratio of the train. Final answer: an idler gear changes the direction of rotation of the output gear, and/or increases the distance between shafts, without changing the overall velocity ratio.

[1] the idler gear changes/reverses the direction of the driven gear compared with a direct two-gear mesh (or allows the shafts to be spaced further apart); [1] correctly states the idler gear does not change the overall velocity ratio of the gear train.

Level of response guidance (indicative content, to be marked using the 5-band QWC rubric below): Scale of production/tooling cost - injection moulding requires an expensive precision steel mould, which is only economically justified when its cost can be spread across a very large number of identical units; a one-off prototype cannot justify this cost. Unit (per-part) production time and cost - once tooling exists, injection moulding produces each part in seconds at very low unit cost, ideal for high volume; low-volume/one-off methods such as 3D printing, vacuum forming over a simple pattern, or hand fabrication have a much higher cost and time per part but no tooling cost, suiting a single prototype. Consistency/quality - injection moulding gives highly repeatable, identical parts, which is essential when 100,000+ units must be interchangeable; a one-off prototype does not need this level of part-to-part consistency. Design flexibility/lead time - tooling for injection moulding takes time to design and manufacture and is expensive to modify once made, so it is unsuitable while a design may still change, as is typical for a prototype; additive manufacture/hand methods allow the design to be altered freely between iterations. Material and finish considerations - the chosen process must still be compatible with the required material and surface finish of the final component in both cases. Final answer: for very high volume, injection moulding is selected because its high tooling cost is offset by very low, consistent unit cost and production speed; for a single prototype, a low/no-tooling process such as 3D printing is preferred because it avoids the mould cost and allows design changes, despite being slower and more expensive per part.

Level of response mark scheme (10 marks). Excellent (9-10 marks): detailed, accurate discussion covering at least 4 relevant factors (tooling cost, unit cost/time, consistency/quality, design flexibility/lead time, material/finish) with clear comparison between high-volume and one-off production and correct use of technical terminology throughout; high quality of written communication with few if any errors. Good (7-8 marks): covers 3-4 relevant factors with generally accurate comparison; mostly correct terminology; good written communication with minor errors. Satisfactory (5-6 marks): covers 2-3 relevant factors; comparison present but may be one-sided or underdeveloped; written communication is understandable with some errors. Limited (3-4 marks): covers 1-2 relevant factors, largely as unlinked statements rather than a discussion/comparison; written communication has noticeable errors that partially hinder meaning. Basic (1-2 marks): very limited/generic response (e.g. names injection moulding only, with little or no justification); significant errors in written communication. 0 marks: no creditable response.