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Q: What does SEAB O-Level Physics (6091, 2026): The Definitions & Formulae Guide cover? A: A syllabus-faithful, exam-ready list of definitions and relationships explicitly required in Singapore's O-Level Physics (6091, 2026), plus clarifications on common extras.
This post distills the main definitions and formulae that the SEAB O-Level Physics (6091, 2026 syllabus) explicitly expects you to know and apply. Where a concept is commonly taught but not printed as a “recall/apply” relationship in the syllabus, I label it accordingly so you don't memorise more than you need.
Stay Connected
Use our O-Level Physics Experiments hub to keep formula drills synced with the hands-on investigations you'll meet in Paper 3.
At-a-glance formula sheet
Units are SI unless stated. Use the value of g given in the question. If none is given, follow your school’s convention (many schools use g=10ms−2
Critical angle and total internal reflection (concepts).
Image characteristics for a thin converging lens: real/virtual, upright/inverted, magnified/diminished; draw and interpret ray diagrams.
Focal length of a converging lens (concept/use).
Electricity
Electric field: region where a charge experiences a force.
Current: rate of flow of charge A.
Electromotive force (e.m.f.): work done per unit charge by the source around a complete circuit V.
Potential difference (p.d.): work done per unit charge across a component V.
Practical electricity (safety)
Live, neutral, earth (ground) wires: meanings and roles.
Mains plug wiring; switches/fuses on the live wire; earthing and double insulation.
Magnetism & electromagnetism
Magnetic field (field lines and patterns around magnets, straight conductors, and solenoids).
Electromagnetic induction
Qualitative induction (what changes increase induced e.m.f., sketching AC output).
(Mnemonic names like “Fleming's right-hand rule” are not required by the spec, though left-hand rule is commonly discussed for motors.)
Radioactivity
Nuclide notation ZAX (interpret A,Z).
Alpha, beta, gamma: nature and effects on A and Z.
Half-life (meaning and use in simple calculations).
Nuclear fission and fusion (meanings).
Activity A (symbol/unit recognition; formal A=λN not required).
Practice Quiz
Check your memory of must-know definitions and equations-while spotting the "common extras" you can deprioritise.
Worked “formats” you will actually use
1) Hydraulics / fluids
p=AF and p=hρg appear often in connected-container or manometer contexts.
2) Energy chains & power
Combine P=VI with E=VIt to move between power, current, voltage, time, and energy.
Billing: convert W ↔ kW and s ↔ h cleanly before multiplying by the tariff.
3) Graphing to linear form
Many lab relationships need rearrangement to y=mx+c so that the gradient/intercept equals a physical constant. Label axes with units and propagate uncertainties sensibly.
4) Lens work
Use ray diagrams for object>f, =f, and <f. Quote image properties rather than plugging a magnification formula (not required).
5) Radioactive decay questions
Balance nuclide equations for α and β (β−) increases Z by 1, A unchanged; α decreases A by 4 and Z by 2; γ leaves A,Z unchanged.
Half-life: read off from tables/curves or apply stepwise halving; avoid introducing λ unless given.
“We added these after review”
From our discussion, these are part of 6091 and worth putting on your sheet:
Internal energy (definition).
Terminal velocity (concept under motion with air resistance).
Electrical energy & cost in kWh (plus P=VI, E=VIt).
Nuclide equations for α, β, γ and half-life calculations.
Commonly taught but not printed as recallable relations in 6091
You may still learn/use these in class, but they're not listed as formulae to memorise in this syllabus:
f=T1 (frequency-period)
Critical angle formula:sinc=n1
Magnification and thin-lens equation f1=u1+v1
Average velocity = displacement/time (only average speed is printed)
ResistivityR=ρAℓ
Radioactive decay lawN=N0(21)t/T1/2
Named mnemonics like right-hand grip and Fleming's right-hand rule (qualitative ideas are examined, but the mnemonics themselves aren't specified)
Final notes
Stick to SI units and clear significant figures.
When in doubt, draw the diagram (free-body, ray, circuit, field lines) and map each quantity to the appropriate relationship.
The syllabus emphasises interpretation of graphs, proportional reasoning, and linking concepts (e.g., energy → power → cost), as much as raw formula recall.
If you'd like this turned into a printable A4 one-page reference PDF (with units and a small index), I can generate it now.
