Numbers
AQA A-Level Physics 7408
Measurements and Their Errors
Particles and Radiation
Topic overviewConstituents of the atomStable and unstable nucleiParticles, antiparticles and photonsParticle interactionsClassification of particlesQuarks and antiquarksApplications of conservation lawsThe photoelectric effectCollisions of electrons with atomsEnergy levels and photon emissionWave-particle duality
Waves
Mechanics and Materials
Electricity
Further Mechanics and Thermal Physics
Fields and Their Consequences
Topic overviewFieldsNewton's lawGravitational field strengthGravitational potentialOrbits of planets and satellitesCoulomb's lawElectric field strengthElectric potentialCapacitanceParallel plate capacitorEnergy stored by a capacitorCapacitor charge and dischargeMagnetic flux densityMoving charges in a magnetic fieldMagnetic flux and flux linkageElectromagnetic inductionAlternating currentsTransformers
Nuclear Physics
AstrophysicsOptional topic
Topic overviewAstronomical telescope consisting of two converging lensesReflecting telescopesSingle dish radio telescopes, I-R, U-V and X-ray telescopesAdvantages of large diameter telescopesClassification by luminosityAbsolute magnitude, MClassification by temperature, black-body radiationPrinciples of the use of stellar spectral classesThe Hertzsprung-Russell (HR) diagramSupernovae, neutron stars and black holesDoppler effectHubble's lawQuasarsDetection of exoplanets
Medical PhysicsOptional topic
Topic overviewPhysics of visionDefects of vision and their correction using lensesEar as a sound detection systemSensitivity and frequency responseDefects of hearingSimple ECG machines and the normal ECG waveformUltrasound imagingFibre optics and endoscopyMagnetic resonance (MR) scannerThe physics of diagnostic X-raysImage detection and enhancementAbsorption of X-raysCT scannerImaging techniquesHalf-lifeGamma cameraUse of high-energy X-raysUse of radioactive implantsImaging comparisons
Engineering PhysicsOptional topic
Turning Points in PhysicsOptional topic
Topic overviewCathode raysThermionic emission of electronsSpecific charge of the electronPrinciple of Millikan's determination of the electronic charge, eNewton's corpuscular theory of lightSignificance of Young's double slits experimentElectromagnetic wavesThe discovery of photoelectricityWave–particle dualityElectron microscopesThe Michelson-Morley experimentEinstein's theory of special relativityTime dilationLength contractionRelativistic mass and energy
ElectronicsOptional topic
Topic overviewMOSFET (metal-oxide semiconducting field-effect transistor)Zener diodePhotodiodeHall effect sensorDifference between analogue and digital signalsLC resonance filtersThe ideal operational amplifierInverting amplifier configurationNon-inverting amplifier configurationSumming amplifier configurationReal operational amplifiersCombinational logicSequential logicAstablesPrinciples of communication systemsTransmission mediaTime-division multiplexingAmplitude (AM) and frequency modulation (FM) techniques
Engineering Physics
Engine cycles
- 6 things to know
- Paper 3, section B
Overview
The four-stroke petrol and diesel cycles, indicator diagrams, and input, brake and friction power.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What is the brake power formula, what do its symbols mean, and how is friction power defined?
Numbers
What does overall efficiency measure, and what does friction power represent?
Numbers
How are thermal and mechanical efficiency calculated, and what does the latter represent?
Key term
In a four-stroke engine, how many crankshaft revolutions are required for each cylinder to complete one power stroke?
Key term
How can indicator diagrams be used to assess efficiency losses in a real engine?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What happens during the induction stroke of a four-stroke petrol engine?
Model answer
The fuel-air mixture is drawn into the cylinder as the piston moves downward with the intake valve open.
- 2
Describe what occurs during the compression stroke in a four-stroke petrol engine.
Model answer
The piston moves upward with both valves closed, compressing the fuel-air mixture to a smaller volume and increasing its pressure and temperature.
- 3
What takes place during the power stroke of a four-stroke petrol engine?
Model answer
The compressed fuel-air mixture is ignited, causing rapid expansion of hot gases that push the piston downward, doing work on the crankshaft.
- 4
What is the purpose of the exhaust stroke in a four-stroke petrol engine?
Model answer
The piston moves upward with the exhaust valve open, expelling the burnt gases from the cylinder.
- 5
How is ignition achieved in a petrol engine, and under what thermodynamic condition does it occur?
Model answer
Ignition is achieved by a spark plug, and it occurs at approximately constant volume near top dead centre.
- 6
How does the ignition method in a diesel engine differ from that in a petrol engine?
Model answer
In a diesel engine, fuel is injected into highly compressed hot air and ignites spontaneously due to the high temperature from compression, rather than requiring a spark plug.
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