WJEC A-Level Design and Technology Unit 3 Technical Principles: a complete overview of smart materials, structures, mechanisms, electronics, design theory and sustainability

What Unit 3 actually demands

Unit 3 Technical Principles is the A2 written paper, and it takes the technical knowledge of Unit 1 to greater depth while adding the design theory the qualification needs at A2. It spans both specialist technical principles (smart materials, composites, structures, mechanisms, electronics) and designing and making principles (design strategies and communication, design influences, design for manufacture, life cycle assessment and the wider impact of design). It is the most content-heavy unit, and it rewards precise definitions, clear systems and structural reasoning, and a few standard calculations.

This guide walks through the ten topics of the unit, then sets out the exam patterns WJEC repeats. Each topic has a matching dot-point page with worked exam questions; this overview ties them together.

Smart and modern materials

Smart materials respond reversibly to a stimulus and the response is the function: shape memory alloys (heat), thermochromic and photochromic pigments (heat and light), quantum tunnelling composite (pressure), piezoelectric (stress and voltage) and electroluminescent (voltage). Modern materials are newly developed (polymorph, precious metal clay). The exam wants the stimulus, the response and a product use.

Composite materials and technical textiles

A composite combines a reinforcement (carries load) and a matrix (binds and protects) for a high strength-to-weight ratio: GRP, carbon fibre reinforced polymer, reinforced concrete, plywood. Technical textiles are engineered for a function: Gore-Tex (waterproof and breathable), Kevlar (cut and impact resistant), microfibres and conductive fabrics.

Structures, forces and stresses

Forces in structures are tension, compression, shear, bending and torsion; stress is force per unit area. Structures are strengthened efficiently by triangulation, efficient cross-sections (I-beams, box sections), folding, corrugating and webbing, and lamination - placing material where the forces are.

Mechanical devices and movement

The four motions are linear, rotary, reciprocating and oscillating. Mechanisms change motion and force: levers and linkages (mechanical advantage), gears (gear ratio = driven teeth / driver teeth), pulleys, cams and followers (rotary to reciprocating) and cranks and sliders. Gaining force always costs speed.

Electronic systems and programmable components

Electronic products are designed as input - process - output systems. Inputs are sensors (switch, LDR, thermistor, PIR); the process is increasingly a programmable microcontroller; outputs (LED, buzzer, motor) often need a driver. Microcontrollers make products smaller, smarter and reprogrammable.

Design thinking and communication

Strategies: user-centred, iterative and collaborative design. Communication: freehand sketching (ideation), orthographic and pictorial drawing, modelling and prototyping, and CAD and CAM (accurate editable models that drive machines directly). Each method suits a stage from idea to manufacture.

Design influences

Movements (Bauhaus and Modernism - form follows function; Art Deco; Memphis; Arts and Crafts) and designers (such as Dieter Rams) shape products' styling, function and values, past and present. Analysing influence means linking a product's form, function and decoration to a movement or designer.

Design for manufacture and scales of production

Scales are one-off, batch, mass and continuous; scale drives design and tooling. Design for manufacture and assembly simplifies and reduces parts. Tolerances (permitted range of a dimension) give interchangeable parts; quality control, jigs, templates and standard components give consistent, accurate, fast production.

Life cycle assessment and design for disassembly

An LCA assesses impact across five stages (raw materials, manufacture, distribution, use, disposal), showing where impact falls so effort is targeted. Design for disassembly, repair and recycling lowers end-of-life impact through non-permanent joints and fewer material types.

The wider impact of design

Designers carry social, moral and ethical responsibilities: genuine need, fair and safe labour, environmental harm and e-waste, planned obsolescence, inclusive design (ergonomics and anthropometrics), standards and legislation, and enterprise (viability). Responsible design balances people, planet and profit.

How Unit 3 is examined

Unit 3 is an A2 written paper on technical principles. Questions come straight from the specification, mixing short recall with extended discuss-and-evaluate questions and a few calculations (gear ratio, mechanical advantage). Be ready to apply the systems approach, reason about forces and structures, and discuss design movements, sustainability and the designer's wider responsibilities.

The ten topics, dot point by dot point

Each topic has a dot-point answer page with worked exam questions and cross-links. Browse them from this unit overview and the subject hub.

For the official specification

WJEC publishes the full specification, past papers and mark schemes at wjec.co.uk. Always revise from the current specification and WJEC's own past papers, because question style is board-specific.