Key term
OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Topic overviewAnalogue and digital measuring instrumentsImproving accuracy with repeat timing, fiducial markers and plumb linesTiming, calipers and micrometersConstructing and testing circuitsSignal generators and oscilloscopesGenerating and measuring wavesData loggers, modelling software and ionising radiation
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Topic overviewProgressive waves and their propertiesThe wave equationReflection, refraction and diffractionWave graphs and intensityThe electromagnetic spectrumPolarisationRefraction and refractive indexCritical angle and total internal reflectionThe principle of superpositionInterference, coherence and path differenceTwo-source interference, Young's double-slit experiment and the diffraction gratingForming stationary wavesStationary waves on strings and in air columnsMeasuring the speed of soundNode spacing, amplitude and phase in stationary wavesHarmonics and the fundamental mode
Quantum Physics
Thermal Physics
Topic overviewThermal equilibrium and absolute temperatureThe kinetic model of solids, liquids and gasesBrownian motion and internal energySpecific heat capacityMeasuring specific heat capacitySpecific latent heatMeasuring specific latent heatMoles, the Avogadro constant and kinetic theoryGas laws, the ideal gas equation and r.m.s. speedMaxwell-Boltzmann distribution, Boltzmann constant and internal energy
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Topic overviewThe solar system and the birth of a starThe death of a low-mass starSupernovae, neutron stars and black holesThe Hertzsprung-Russell diagramEnergy levels and emission spectraAbsorption spectra and spectral linesPhoton energy and the diffraction gratingWien's law and Stefan's lawAstronomical distances, parallax and the cosmological principleDoppler shift and Hubble's lawThe expanding universe and the Big BangEvidence for the Big Bang and dark energy
Capacitors
Topic overviewCapacitance and charging a capacitorCapacitors in seriesCapacitors in parallel and combined circuitsEnergy stored by a capacitorCharging and discharging through a resistorInvestigating capacitor dischargeThe time constantIterative modelling, exponential decay and the constant-ratio property
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Topic overviewAlpha-particle scattering and the nuclear modelProton number, nucleon number and isotopesThe strong nuclear force and nuclear radiusParticles, antiparticles and hadronsLeptons and the quark modelQuark composition and chargesBeta decay in the quark modelRadioactive decay and the three radiationsNuclear decay equationsActivity, decay constant and half-lifeExponential decay and radioactive datingMass-energy equivalenceAnnihilation, mass defect and binding energyBinding energy per nucleon and induced fissionThe fission reactor and nuclear wasteNuclear fusion and balancing nuclear equations
Physical Quantities and Units
- 3 subtopics
- 9 things to know
- All three papers
What Physical Quantities and Units covers
How physics measures things: quantities and their units, the S.I. base and derived units, prefixes, and the check that an equation balances dimensionally.
Where it is assessed
All three papers
Practical skills and physical quantities, assumed throughout.
Check the OCR specification ↗The 3 subtopics
Each one has its own page.
- Physical quantities, estimation and unit conversionsRecall questions on the numerical value and unit of a physical quantity, order-of-magnitude estimates and their assumptions, and converting squared and cubed units with prefixes.Open →
- S.I. base and derived unitsRecall questions on the base quantities and their units, and on how derived units are built from them.Open →
- Prefixes, homogeneity and labelling conventionsRecall questions on the prefixes from pico to tera, checking whether an equation is homogeneous and what that does not prove, and labelling graph axes and table columns as 'quantity / unit'.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
How do you check that a physical equation balances dimensionally?
Key term
What are the two parts that make up any physical quantity?
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Give an example of how a derived unit is constructed from base units.
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What is the first step when checking whether a physical equation is homogeneous?
Who and when
How should the column headings in a data table be formatted according to scientific convention?
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Explain the general principle for converting a unit with a prefix when the unit is squared.
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What are derived units?
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After expressing each term in base units, what must you do next to test homogeneity?
Take Physical Quantities and Units further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Scalar vs Vector
Scalar: quantity with magnitude only. Vector: quantity with magnitude and direction.
Questions from this topic
Each one with the model answer underneath.
- 1
What are the two parts that make up any physical quantity?
Model answer
A numerical value and a unit.
- 2
In the expression '9.81 m s⁻²', which part is the numerical value?
Model answer
9.81
- 3
In the expression '9.81 m s⁻²', which part is the unit?
Model answer
m s⁻²
- 4
When estimating a physical quantity, to what level of precision should the estimate typically be expressed?
Model answer
To an appropriate order of magnitude (power of ten).
- 5
Why are reasonable assumptions important when making order-of-magnitude estimates?
Model answer
They allow sensible approximations of unknown values, enabling a realistic estimate of the final quantity.
- 6
When converting cm³ to m³, why must the conversion factor be cubed?
Model answer
Because each linear dimension is converted (1 cm = 10⁻² m), and volume involves three dimensions, so the factor becomes (10⁻²)³ = 10⁻⁶.
What is inside Levo
Six ways to work the same material.
Physical Quantities and Units revision questions
- What does Physical Quantities and Units cover in OCR A-Level Physics A?
- 3 subtopics: physical quantities, estimation and unit conversions, s.i. base and derived units and prefixes, homogeneity and labelling conventions. Each one has its own page with questions and model answers.
- How is Physical Quantities and Units organised?
- By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Physical Quantities and Units, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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