0625 IGCSE Physics · Paper 1 Core · One-page

The 10 mistakes that cost Core Paper 1 candidates marks.

Compressed from five years of Cambridge examiner reports (2021–2025). Print it. Stick it on the wall.

40 questions · 45 minutes · no negative marking · never leave a blank

The 10 traps

Ranked by examiner-report frequency · 0625/11·12·13

Free fall = constant g. Every object accelerates at g (9.8 or 10 m/s²). Heavier does not fall faster; it does not speed up more as it drops. Every series

Distance = area under a speed–time graph. d = v×t only at constant speed. Split into triangles + rectangles. Gradient = acceleration, not area. Recurring

Half-life = time to half the start value. Read half the y-axis value, drop to the time axis. Fallen to 1/8? That is 3 half-lives, not total÷8. Recurring

Parallel resistors < the smaller one. Never the average. More paths ⇒ more current ⇒ lower total R. Persistent

NOT · EXCEPT · ONLY. Underline the command word before you read A–D. Decide what you are looking for first. Every series

Convert units first — min→s is #1. Also mA→A (÷1000), mm→m, cm³→m³, kW→W. Especially in E=Pt, Q=It. Every year

Series current is the same everywhere. It is not "used up" by a lamp. Charge is conserved; current only splits at parallel junctions. Persistent

Plane-mirror image: virtual, upright, laterally inverted. Not real, not upside-down. Behind the mirror, as far back as the object is in front. Recurring

Mass (kg) vs weight (N). Weight = mg, a force. Mass is matter. g = force per unit mass (N/kg) — not the weight. Recurring

There-and-back: halve the time. Echo / sonar / radar give the round-trip time — halve it before d = v×t (or halve the answer). Recurring

6 habits that fix most of them

Cover the options. Solve first. Reading A–D first leads to back-fitting — the examiners' #1 complaint.
Eliminate two, then choose. Even halving the field doubles your odds.
Write the equation before substituting. Stops V/I vs I/V and ρ = m/V going in upside-down.
Convert every unit to SI at the start. min→s; mm→m; cm³→m³; mA→A.
Sanity-check the magnitude. Adult ≈ 60–80 kg; speed of sound ≈ 340 m/s. A wild number is a wrong number.
Never leave a blank. No negative marking — eliminate, then pick.

Last-week checklist

Tick when you can do it cold

Mass (kg) vs weight (N); W = mg

Density ρ = m/V (kg/m³)

Pressure p = F/A (Pa); in a liquid p = ρgh

Convert min→s, mm→m, cm³→m³, mA→A

Speed–time graph: area = distance; gradient = acceleration

Distance–time graph: gradient = speed

Free-fall acceleration is constant

Average speed = total distance ÷ total time

Equilibrium = zero resultant force AND zero moment

Moment = F × perpendicular distance

Change of state → temperature constant

Kelvin = °C + 273

Dull black = best emitter / absorber of radiation

All EM waves: same speed in vacuum

Sound = longitudinal; all angles from the normal

TIR above the critical angle → no refracted ray

Resistance = V/I (not gradient for non-ohmic)

Series: I same, PD adds. Parallel: PD same, I adds, R < smallest

Thermistor T↑ → R↓; LDR light↑ → R↓

Fuse just above operating current; transformer needs a.c.

α = He nucleus; β = electron from nucleus; γ = EM wave

Half-life: 1/2, 1/4, 1/8 at 1, 2, 3 half-lives; decay is random

Exam morning, in order

Read each question in full before looking at the options.
Underline NOT · EXCEPT · ONLY.
Solve cleanly, then match to the options.
Convert units, then magnitude-check before circling.
If stuck — eliminate, mark, move on. Come back.
Never leave a blank.

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