Cambridge IGCSE Physics 0625/42 is the May/June 2026 Paper 4 (Extended Theory), variant 2. It lasts 1 hour 15 minutes, is worth 80 marks and is sat by every Extended candidate. It had eleven compulsory questions, none worth more than 10 marks, so it moved quickly across the whole syllabus; the biggest was Question 8 on electric fields and a thermistor circuit. This guide goes through the paper question by question and shows what the official mark scheme gave marks for. The paper and its mark scheme are free on the Tutopiya Learning Portal.

For an overview of all six 0625 papers from this series, see IGCSE Physics 0625 May/June 2026 past papers: what came up and how it was marked.

0625/42 at a glance

Question	Topic	Marks	Main command word
1	Motion: a car’s speed-time graph, distance, vector quantities	8	State, calculate
2	A satellite’s orbit, a rocket’s acceleration, gas pressure, kelvin to °C	8	Calculate, explain
3	An electric shower: mass, specific heat capacity, power	7	Show that, calculate
4	Impulse, a student landing from a jump, pressure	8	Explain, calculate
5	Evaporation and cooling, drying clothes	5	Explain, state
6	Principal focus, a converging lens ray diagram, the EM spectrum	6	Draw, complete
7	How a loudspeaker works, wavelength, ultrasound	6	Complete, calculate
8	Electric fields, a thermistor and relay circuit, charge	10	Complete, draw
9	Isotopes, a carbon-14 decay curve, background radiation	6	Sketch, state
10	Nuclear fission and power stations, nuclear compared with solar	8	Describe, state
11	Space: Earth, Sun and Moon timings, Jupiter’s orbit, the Hubble constant	8	Show that, calculate
	Total	80

Question-by-question walkthrough

Question 1: a car’s speed-time graph and vectors (8 marks)

The graph rose in a straight line through A to B (14 m/s at 18 s), curved up to a flat section from C to D, then curved down steeply to E.

• Motion in three sections (3 marks): A to B is constant acceleration; C to D is constant speed (constant velocity, steady speed); D to E is increasing deceleration, because the curve gets steeper. Non-uniform or changing deceleration was accepted for D to E, but “decreasing acceleration” contradicted the mark, and “zero acceleration” for C to D was too vague.
• Distance from 0 to 18 s (2 marks): the area under the graph is a triangle, ½ × 18 × 14 = 126, so 130 m to 2 significant figures.
• What makes a vector (1 mark): it has magnitude and direction.
• Underlining the vectors (2 marks): acceleration, electric field strength and weight. Three correct earned 2 marks and two correct earned 1. Underlining extra, wrong quantities (energy, mass or time) cancelled the credit under the list rule.

Question 2: a satellite, a rocket and a helium balloon (8 marks)

• Direction of the force on an orbiting satellite (1 mark): towards the centre of the orbit, or perpendicular to its motion. “Towards the Earth” was too vague.
• Rocket’s initial acceleration (3 marks): the resultant force is the thrust minus the weight: 1.9 × 10⁵ − (1.5 × 10⁴ × 9.8) = 43 000 N. Then a = F ÷ m = 43 000 ÷ 1.5 × 10⁴ = 2.9 m/s². Dividing the thrust by the mass without subtracting the weight gives 13 m/s², which the scheme named as a special case worth 2 marks. Using g = 10 gave 2.7 m/s², accepted only if the working showed it clearly.
• Gas pressure in terms of particles (3 marks): two marks from: the particles move fast (they have kinetic energy or momentum), they collide with the walls of the balloon, and pressure is the force from these collisions per unit area. The third mark was for linking the collisions to a force on the walls, or to the particles’ change of momentum when they hit the walls. Saying the particles “move faster” or “gain energy” was ignored.
• 228 K in °C (1 mark): 228 − 273 = −45 °C.

Question 3: an electric shower (7 marks)

Water entered at 15 °C and left at 38 °C.

• Show that 18 kg flows in 4.0 minutes (2 marks): mass = density × volume, and the volume is the flow rate × time, so 1000 × 0.0045 × 4.0 = 18 kg. As a “show that”, the equation had to be written in words or symbols for the first mark.
• Energy to heat the water (2 marks): E = mcΔθ = 18 × 4200 × 23 = 1.7 × 10⁶ J. Using Q for energy or t for the temperature change was ignored, so the symbols matter less than the numbers.
• Power (2 marks): P = E ÷ t, with the time in seconds: 1.7 × 10⁶ ÷ 240 = 7100 W (7200 W and 7300 W were also accepted, and the scheme allowed error carried forward from the energy).
• Why the water could come out hotter at the same power (1 mark): the water going in is warmer, or less water flows through each minute. “The water is slower” and “heated for longer” were too vague.

Question 4: impulse and pressure (8 marks)

• Define impulse in words (1 mark): force × time (change of momentum was also accepted). It had to be in words; “mass × change in velocity” was too vague.
• Force on a student landing (2 marks): a 55 kg student moving at 4.6 m/s stops in 0.95 s, so F = Δp ÷ t = (55 × 4.6) ÷ 0.95 = 270 N.
• Why bending the knees prevents injury (3 marks): the impact lasts longer; the impulse (change of momentum) is the same; so the force is smaller. The “same change of momentum” point had to be made before the “smaller force” mark could be given.
• Pressure under a standing student, with unit (2 marks): p = F ÷ A = 530 ÷ 380 = 1.4 N/cm². Converting the area to square metres and giving 1.4 × 10⁴ Pa (or N/m²) was equally correct. The unit is part of the answer mark, so a number with no unit loses it.

Question 5: evaporation (5 marks)

• Why wet skin cools, in terms of particles (3 marks): thermal energy transfers from the skin to the water; the more energetic (faster) particles escape from the surface of the water; the particles left behind have less kinetic energy on average, so the temperature falls. “The particles vibrate” was ignored.
• Two factors affecting how fast clothes dry (2 marks): air temperature, wind, and the surface area of the clothes. Humidity, sunshine or cloud cover, and the colour of the clothes were also accepted.

Question 6: lenses and the EM spectrum (6 marks)

• Definition of principal focus (2 marks): the point where rays parallel to the principal axis converge after passing through the lens. Leaving out “parallel to the principal axis” (just “parallel rays converge”) dropped the answer to 1 mark. “Meet” or “intersect” were accepted in place of “converge”.
• Ray diagram (3 marks): the full-scale diagram had the object beyond F on the left. Two marks were for any two correct rays from the top of the object: parallel to the axis then through F on the right; straight through the centre of the lens; or through F on the left then parallel to the axis. The third mark was for drawing the image from where the rays cross down to the axis, pointing the right way and labelled I. Extra incorrect rays contradicted the marks.
• Lowest-frequency EM region (1 mark): radio waves.

Question 7: the loudspeaker (6 marks)

• How a loudspeaker works (3 marks): the changing magnetic field comes from the alternating current in the coil; it interacts with the field of the permanent magnet; the vibrating cone makes the air (particles) vibrate. “Induced current” contradicted the first mark.
• Wavelength with unit (2 marks): λ = v ÷ f = 340 ÷ 440 = 0.77 m.
• Define ultrasound (1 mark): sound with a frequency above 20 kHz, or above the range of human hearing.

Question 8: electric fields and a thermistor circuit (10 marks)

• Define an electric field (2 marks): a region where a charge (charged particle) experiences a force. Naming one particle, such as “an electron”, was too vague, and any mention of magnetism contradicted the mark.
• Field between parallel plates (2 marks): four evenly spaced lines, perpendicular to the plates and touching both; and at least one arrow pointing from the positive plate to the negative plate, with no wrong arrows.
• Component X (1 mark): a fuse.
• Why the lamp lights when it gets warmer (3 marks): the resistance of the thermistor decreases; the p.d. across the relay coil increases, and its magnetic field gets stronger; the coil attracts the switch, closing the lamp circuit. Writing “armature” for the switch was ignored.
• Charge through the lamp (2 marks): Q = It = 3.2 × 120 = 380 C.

Question 9: carbon-14 and background radiation (6 marks)

• Isotopes (1 mark): same number of protons, different number of neutrons. Both halves were needed for the mark, and mentioning electrons contradicted it.
• Sketch the decay of carbon-14 over 15 000 years (3 marks): the tree starts with 16 µg and the half-life is 5700 years. One mark for a smooth curve starting at 16 µg that gets less steep, one for a curve that never reaches the time axis, and one for a correctly plotted point, such as 8 µg at 5700 years or 4 µg at 11 400 years (2.58 µg at 15 000 years was also accepted). The scheme also flagged one trap: a value of 2.6 µg at 15 000 years obtained from 15 000 ÷ 5700 counted as a contradiction, so plot a point at a whole number of half-lives instead.
• Radiation always present (1 mark): background radiation.
• One significant source (1 mark): radon gas, rocks and buildings, food and drink, or cosmic rays. Nuclear weapons testing and medical procedures were ignored, and the cosmic microwave background contradicted the mark.

Question 10: nuclear power (8 marks)

• Fission (3 marks): a neutron is absorbed by a heavy nucleus; the nucleus splits into smaller nuclei; a large amount of energy is released. “Energy is created” contradicted the last mark.
• From heat to electricity (2 marks): thermal energy heats water to make steam at high pressure, which drives a turbine connected to the generator.
• Nuclear against solar cells (2 marks): an advantage is that nuclear works 24 hours a day and does not depend on the Sun or the weather. A disadvantage is hazardous waste that must be stored for a long time, the danger of a radiation leak, being non-renewable, or the cost of building and decommissioning. “Cost” without detail was too vague.
• A resource not powered by the Sun (1 mark): tidal or geothermal. “Tidal waves” contradicted the mark.

Question 11: space physics (8 marks)

• Matching events to times (2 marks): light took 8.3 minutes to reach the Earth from the Sun (the example given). The Earth orbits the Sun in 365 days, rotates on its axis in 24 hours, and the Moon orbits the Earth in about 1 month. All correct scored 2 marks; one or two correct scored 1.
• Show that Jupiter’s period is 11.9 years (3 marks): T = 2πr ÷ v. Then 2π × 7.78 × 10⁸ km ÷ 4.70 × 10⁴ km/h = 104 000 hours, and dividing by 24 × 365 = 8760 hours in a year gives 11.87 years. Each step was a separate mark, so the hours-to-years conversion has to be shown.
• Define a light-year (1 mark): the distance light travels (in a vacuum) in one year.
• Speed of a galaxy (2 marks): v = H₀d. Convert 1.6 × 10⁸ light-years to metres using 9.5 × 10¹⁵ m per light-year, then v = 2.2 × 10⁻¹⁸ × 1.6 × 10⁸ × 9.5 × 10¹⁵ = 3.3 × 10⁶ m/s. A wrong light-year conversion still earned the equation mark.

Where the marks are on 0625/42

• Calculations carried 25 of the 80 marks: 19 on “calculate” parts, 5 on the two “show that” parts (3(a)(i) and 11(b)) and 1 on the kelvin conversion in 2(b)(ii). Almost every question had one.
• Recall carried 13 marks: the “state” and “identify” parts, such as the motion in 1(a)(i), evaporation factors, the fuse and the energy resources.
• Drawing, sketching and matching carried 12 marks: the vector underlining, the ray diagram, the field lines, the carbon-14 curve and the space matching.
• Completing sentences carried 10 marks, including the loudspeaker and the thermistor circuit, which reward exact physics words such as “permanent magnet” and “resistance decreases”.
• Explain and describe questions carried 12 marks: the 3-mark answers on gas pressure, bending knees, evaporation and fission. Each one is three linked points, one mark each.
• Definitions carried 7 marks: impulse, principal focus, ultrasound, electric field and light-year. These are learnable word for word.
• Suggest carried 1 mark (3(b)).

How to self-mark 0625/42 with the mark scheme

1. Learn the mark types first. An A mark is for the correct final answer, C marks are for the equation and substitution when the answer is wrong, B marks stand alone, and an M mark must be earned before the mark that follows it (as in 4(b)(ii), where “same change of momentum” comes before “smaller force”). SC means a special case, such as the 13 m/s² rocket answer.
2. Check the final answer before the working. A correct answer scores all the marks, except on “show that” questions, where the working is the answer. In 11(b), 11.9 years on its own earns nothing.
3. Check units and significant figures. 7(a)(ii) and 4(b)(iii) asked for the unit, and the answer mark depends on it. The scheme expects the significant figures in its final answer, so 126 m should become 130 m.
4. Apply the list rule. In 1(b)(ii), every extra wrong quantity you underline uses up a place and can cancel a correct one.
5. Look for the R, I and CON notes. “Decreasing acceleration” in 1(a)(i), “induced current” in 7(a)(i) and “energy is created” in 10(a)(i) all contradicted otherwise correct answers.
6. Log each lost mark as missing knowledge, a wrong conversion or unit, a misread command word or a careless slip, and revise in that order.

Sit 0625/42 as a timed mock

The paper allows 75 minutes for 80 marks, a little under one minute per mark. A workable plan:

Block	Marks	Time
Question 1	8	7 minutes
Question 2	8	7 minutes
Question 3	7	7 minutes
Question 4	8	7 minutes
Question 5	5	5 minutes
Question 6	6	5 minutes
Question 7	6	5 minutes
Question 8	10	9 minutes
Question 9	6	5 minutes
Question 10	8	7 minutes
Question 11	8	8 minutes
Check, especially units and conversions	–	3 minutes

Question 11 has the heaviest conversions on the paper (hours to years, light-years to metres), so leave it a little extra time.

Other May/June 2026 0625 papers

• 0625 Paper 12 (Core Multiple Choice)
• 0625 Paper 22 (Extended Multiple Choice)
• 0625 Paper 32 (Core Theory)
• 0625 Paper 52 (Practical Test)
• 0625 Paper 62 (Alternative to Practical)

Practise and download

• Download 0625/42 and its mark scheme on the Learning Portal →
• All 0625 May/June 2026 papers: overview and marking patterns
• Try a free IGCSE Physics quiz

Need help with a 0625 topic? Book a free trial lesson with an IGCSE Physics tutor →

Frequently asked questions

What topics were on 0625 Paper 42 May/June 2026? +

Eleven questions: a speed-time graph and vectors; a satellite, a rocket and gas pressure in a balloon; an electric shower; impulse and pressure; evaporation; lenses; a loudspeaker and ultrasound; electric fields and a thermistor and relay circuit; carbon-14 and background radiation; nuclear power; and space physics.

How many marks is 0625/42 and how long is it? +

It is out of 80 marks and lasts 1 hour 15 minutes. Question 8, on electric fields and a thermistor circuit, is the biggest at 10 marks; every other question is worth 5 to 8.

What was the answer to the rocket acceleration question in 0625/42? +

Subtract the weight from the thrust first: 1.9 × 10⁵ − (1.5 × 10⁴ × 9.8) = 43 000 N, then divide by the mass, 1.5 × 10⁴ kg, to get 2.9 m/s². Forgetting the weight gives 13 m/s², which the mark scheme treated as a special case worth 2 of the 3 marks.

How fast was the galaxy moving in 0625/42 Question 11? +

Convert 1.6 × 10⁸ light-years to metres (1 light-year is about 9.5 × 10¹⁵ m), then multiply by the Hubble constant, 2.2 × 10⁻¹⁸ per second. The answer is 3.3 × 10⁶ m/s, worth 2 marks.

Is 0625/42 the Core or Extended paper? +

Extended. Paper 4 is the Extended theory paper, sat alongside Paper 2 (Extended multiple choice) and either Paper 5 or Paper 6. Core candidates sit Paper 3 instead.

Where can I download 0625/42 May/June 2026 and its mark scheme? +

Both are free to download and print on the Tutopiya Learning Portal, on the Cambridge IGCSE Physics 0625 past papers page.

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