Key term
CCEA A-Level Technology and Design 8900
Material Selection and Wood
Metals
Plastics
Composite and Emerging Materials
Processing Materials
Product Analysis and Design Communication
Design for Manufacture, Quality and Safety
Electronic Control SystemsOption A
Topic overviewControl systems, feedback and electronics safetyResistors, Ohm's law and power ratingsCapacitors and RC timingPotential dividers, sensors and comparatorsSwitches, pull-up and pull-down resistorsOutput devices and LEDsTransistors, Darlington pairs and thyristorsLogic gates, truth tables and flip-flops555 monostable and astable timers
Microelectronic Control SystemsOption A
Topic overviewMicrocontroller systems, ADCs and DACsStrain gauges and bridge circuitsOptical switches, encoded discs and Schmitt triggersOp-amp amplifiers and gainZener diodes and voltage regulatorsKarnaugh maps and binary countersSeven-segment, LCD and dot matrix displaysPIC flowcharts and programmingDC motors, stepper motors and driver circuits
Mechanical and Pneumatic ComponentsOption B
Topic overviewOpen and closed loop mechanical and pneumatic controlSafe working with compressed air and mechanismsLevers, linkages and momentsGear types and gear trainsPulleys, belts, chains and shaft fixingsCams, cranks and converting motionCompressed air supply and pneumatic valvesCylinders, shuttle valves, restrictors and reservoirsPneumatic circuits for logic, timing and speed control
Mechanical and Pneumatic SystemsOption B
Topic overviewHydraulics, system limitations and plant safetyTorque, work, power and air consumptionVacuum handling, proximity sensors and 5/3 valvesSequential and cascade pneumatic circuitsCam profiles and follower displacement diagramsGear geometry, pulley blocks and ratchetsToggles, treadles, shafts and couplingsFriction, brakes and clutchesBearings, lubrication and seals
Designing and Manufacturing ProductsOption C
Topic overviewResearch, questionnaires and specificationsIdea generation, critiques and computer simulationManufacturing planning and product evaluationCFRP, GRP, Kevlar and tungsten carbideSmart materials, nanotechnology and biophotovoltaicsIsometric, perspective and assembly drawingLaminating, steam bending, cutting and printing processesRisk assessment and product safety lawScales of production, JIT and cell productionQuality assurance, ISO 9001 and continuous improvementDesign influences and intellectual property rights
Product Design in Industry and SocietyOption C
Topic overviewLife-cycle environmental impact and climate changeThe 6Rs, waste and environmental legislationSustainable metals, plastics and degradable polymersProduct life cycles, consumer types and relaunchesCAD, CAM, 3D scanning and quick-change mouldingMarket pull, technology push and market strategyPrice, place and promotionJigs, fixtures and ICT in quality controlDesign for maintenance, inclusion and scale productionRendering, typography and presentationDyson, Baylis, Memphis and Apple
Product Development
Product and System Design and Manufacture
Electronic Control Systems
Resistors, Ohm's law and power ratings
- 3 things to know
- AS 1 Paper 2
Overview
The resistor colour code and tolerance, the E12 series, Ohm's law and power with worked calculations, power ratings, and series and parallel combinations.
What you need to know
Answer each one before you reveal it.
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Key term
A 1 kΩ resistor is in series with two 2 kΩ resistors in parallel. What is the total resistance?
Key term
How does the four-band colour code give a resistor's value?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How does the four-band colour code give a resistor's value?
Model answer
The first two bands give the first two digits and the third band is the multiplier. The fourth band gives the tolerance, gold for ±5% and silver for ±10%.
- 2
What is the value of a resistor banded brown, black, red, gold?
Model answer
The resistor is 1 kΩ with a tolerance of ±5%. Brown is 1, black is 0 and red adds two zeros, giving 1000 Ω.
- 3
Which colours mark the value of a 47 kΩ resistor?
Model answer
A 47 kΩ resistor is banded yellow, violet, orange. Yellow is 4, violet is 7 and orange adds three zeros.
- 4
Calculate the range of actual values for a 1 kΩ resistor with ±5% tolerance.
Model answer
The actual value can lie anywhere from 950 Ω to 1050 Ω. Five per cent of 1000 Ω is 50 Ω, taken off and added to the nominal value.
- 5
What is the E12 series?
Model answer
The E12 series is a set of twelve preferred resistor values in each decade. The values are 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82. Each value can be multiplied by any power of ten.
- 6
Why are resistors made in preferred values rather than every possible value?
Model answer
The E12 values are spaced so that their ±10% tolerance ranges roughly meet. A small stock of values then covers every possible resistance.
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