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
Reversed heat engines
- 5 things to know
- Paper 3, section B
Overview
Refrigerators and heat pumps, the coefficient of performance, and why it can exceed one.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
When does the temperature-based COP formula apply, and what is Qₕ?
Numbers
How is heat pump COP calculated, and what scale must temperatures use?
Numbers
Why must Celsius not be used in COP formulae, and why can COP exceed one?
Numbers
What is a heat pump's ideal COP in terms of temperatures, why does it deliver more energy than the work put in, and why is a COP above one no breach of energy conservation?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a heat pump and what does it require to operate?
Model answer
A heat pump is a device that transfers thermal energy from a cold reservoir to a hot reservoir, requiring external work input to achieve this transfer.
- 2
Describe the function of a refrigerator in terms of energy transfer.
Model answer
A refrigerator transfers thermal energy from a cold interior to warmer surroundings, requiring external work input.
- 3
What is the practical application of heat pumps in buildings?
Model answer
Heat pumps are used to heat buildings by extracting thermal energy from the environment (such as the ground, air, or water) and transferring it indoors.
- 4
How does a refrigerator maintain a cold space?
Model answer
A refrigerator maintains a cold space by continuously removing thermal energy from it and transferring that energy to the warmer surroundings.
- 5
Define the coefficient of performance for a reversed heat engine.
Model answer
The coefficient of performance (COP) measures the ratio of useful energy transfer to work input for a reversed heat engine.
- 6
State the formula for the coefficient of performance of a refrigerator in terms of heat and work.
Model answer
COP_ref = Q_C / W, where Q_C is the heat removed from the cold reservoir and W is the work input.
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