9702 Paper 3 Practical: Full Marks on Tables, Graphs and Uncertainties

Paper 3, Advanced Practical Skills, is the most predictable paper in Cambridge AS & A Level Physics 9702. The physics changes from paper to paper, and the syllabus states that no prior knowledge of the theory is required. But the skills being assessed, and how the marks are allocated to them, are written out in the syllabus. Students who learn those expectations can pick up marks reliably, whatever the experiment.

Paper 3 at a glance (2025–2027 syllabus)

• 2 hours, 40 marks: two questions, each of 1 hour and 20 marks.
• Weighting: 23% of the AS Level and 11.5% of the A Level.
• Question 1: collect data, plot a graph and draw conclusions.
• Question 2: collect data and draw conclusions, possibly without a graph. The method is deliberately inaccurate, and you must evaluate it and suggest improvements.
• The two questions are set in different areas of physics.

Where the marks are

The syllabus gives minimum mark allocations for each skill:

In each question the remaining 3 marks are allocated across the skills and may vary from paper to paper. The key insight is that Question 2 is mostly about evaluation: identifying limitations and suggesting improvements is worth far more there than in Question 1.

Tables of results

The syllabus sets out clear expectations: - Columns for raw data and calculated values. - Headings with quantity and unit, in the accepted convention. For current in milliamperes, "I / mA" is the usual form. - Consistent precision: if a length is measured to the nearest millimetre, every length in that column should be given to the nearest millimetre, e.g. 2.0 cm, not 2 cm. - Significant figures in calculated values: if the least precise measured quantity has n significant figures, give the calculated value to n or n + 1 significant figures.

Example (original): you measure a p.d. of 1.4 V (2 s.f.) and a current of 0.2350 A (4 s.f.). The resistance should be given to 2 or 3 significant figures, i.e. 6.0 Ω or 5.96 Ω, but not 6 Ω or 5.957 Ω.

Graphs

• Label both axes with quantity and unit, using the same convention as column headings.
• Choose scales so that the points occupy at least half the grid in both directions, using easy steps such as 1, 2 or 5 units per 2 cm.
• Plot points accurately, with markers less than 1 mm in diameter.
• Draw a line of best fit with a balanced scatter of points either side.
• When finding a gradient, use points on the line separated by more than half the length of the line drawn. Show the coordinates you used.
• To find the y-intercept, either read it directly (if the axis starts at zero) or substitute a point and the gradient into y = mx + c.

Uncertainties

The syllabus expects you to: - estimate the absolute uncertainty in a measurement, - convert between absolute and percentage uncertainty, - express the uncertainty in a repeated measurement as half the range of the readings.

Example (original): three timings of 10 oscillations give 2.31 s, 2.35 s and 2.28 s. - Mean = 6.94 / 3 = 2.31 s - Absolute uncertainty = ½ × (2.35 − 2.28) = 0.035 s, about 0.04 s - Percentage uncertainty = 0.035 / 2.31 × 100 ≈ 1.5%

In Question 2 you may also be asked to calculate the percentage difference between two values of a constant and compare it with a given percentage uncertainty, to judge whether a suggested relationship is supported.

Limitations and improvements

This is where Question 2's 10 analysis marks are concentrated, and where answers are most often too vague.

State the quantity and the reason. The syllabus says that for uncertainties in measured quantities, candidates should state the quantity being measured and a reason for the uncertainty. - Weak: "Human error in timing." - Strong: "The time for the ball to fall was difficult to measure because the time interval was very short compared with reaction time."

Match each improvement to a limitation, and make it specific and practical: - Weak: "Use better equipment." - Strong: "Use light gates connected to a data logger to measure the time interval."

Other examples of useful improvements include video recording with a scale and timer, a set square to read a scale at right angles, clamping a component so it does not move, or taking more readings and plotting a graph. "Repeat readings" on its own is rarely credited, because the method already uses two readings.

Managing the two hours

Each question is designed to take 1 hour, and your centre may require you to change over between questions at the half-way point. Use each hour deliberately: - First few minutes: read the whole question, including what you must calculate and plot, before touching the apparatus. - Set up and take one trial reading to check that the method works and the range is sensible. - Collect the full set of readings the question asks for, spread across the widest range the apparatus allows. - Leave time for analysis. Graphs, gradients and conclusions carry marks that are lost if you run out of time. - Record as you go, directly into the table, including repeated readings.

Common mistakes

1. Units missing from column headings, or written in the wrong format.
2. Inconsistent decimal places within a column of raw data.
3. A gradient triangle that is too small.
4. Points that occupy less than half of the graph grid.
5. Limitations given as "human error" or "parallax" with no quantity named.
6. Improvements that do not address the limitations stated.

How to prepare

• Practise in the laboratory where possible. Manipulation marks reward real hands-on experience.
• Rehearse table and graph conventions until they are automatic.
• Build a personal list of limitations and improvements for common set-ups (pendulums, springs, circuits, falling objects, light gates).
• Sit timed papers from the 9702 past papers library, paying particular attention to the confidential instructions and mark schemes.
• Paper 3 skills feed directly into Paper 5. See our guide to 9702 Paper 5 planning.

Practise by topic

Topical PDFs of 9702 past-paper questions, with mark schemes: Electricity · D.C. circuits · Oscillations.

Frequently asked questions

Do I need to know the theory for Paper 3? No. The syllabus states that no prior knowledge of the theory is required.

Is "repeat readings" an acceptable improvement? Usually not on its own. Suggest a specific, practical change linked to a limitation you have identified.

How many significant figures for calculated values? The same as, or one more than, the least precise measured quantity used.

What proportion of the A Level is practical? Paper 3 (11.5%) and Paper 5 (11.5%) together make up 23% of the A Level.

Build practical confidence

Engr. Muhammad Waseem, BS Mechanical Engineering (UET Lahore), has taught Cambridge A Level Physics since 2022. He helps students turn practical conventions into habits, so marks are not lost on presentation.

Sources: Cambridge International AS & A Level Physics 9702 syllabus for examination in 2025–2027: assessment overview, section 5 (Practical assessment) and the Paper 3 mark allocations (https://www.cambridgeinternational.org/Images/664565-2025-2027-syllabus.pdf).

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