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Extended response questions in physics — typically worth 6 marks — require you to construct a sustained, logically structured answer that demonstrates both your physics knowledge and your ability to communicate it clearly. These questions are marked using a levels-based scheme, which means the overall quality of your answer determines your mark, not just the number of individual points you make.
Extended response questions use levels-based marking:
| Level | Marks | Description |
|---|---|---|
| 3 | 5–6 | Comprehensive answer with correct terminology, logical structure, and detailed physics |
| 2 | 3–4 | Some relevant physics but incomplete, partially disorganised, or missing key detail |
| 1 | 1–2 | Basic points with limited detail, significant errors, or poor structure |
| 0 | 0 | No relevant physics content |
To reach Level 3, your answer must:
These ask you to outline how you would investigate a physical quantity. A strong answer includes:
graph TD
A["Describe an Experiment — 6 marks"] --> B["Name specific apparatus"]
B --> C["State IV, DV, and control variables"]
C --> D["Describe step-by-step method"]
D --> E["State what you measure and how"]
E --> F["Explain how to process results"]
F --> G["Include graph: what to plot,\nwhat gradient means"]
G --> H["Mention safety precautions"]
H --> I["State repeat readings → mean"]
Example question: "Describe an experiment to determine the Young's modulus of a metal wire."
Model answer:
Set up a long, thin copper wire (at least 2 m) clamped securely at one end to a rigid support. Measure the original length L using a metre ruler. Measure the diameter d at several points along the wire using a micrometer screw gauge, and calculate the mean diameter. Calculate the cross-sectional area using A = π(d/2)².
Attach a mass hanger to the free end. Add masses in known increments (e.g., 100 g), recording the extension e for each load using a marker on the wire and a ruler (or a travelling microscope for greater precision). Take readings as masses are added and removed to check for elastic behaviour.
Plot a graph of stress (σ = F/A) against strain (ε = e/L). The gradient of the straight-line region equals the Young's modulus. Wear safety goggles in case the wire snaps under tension.
These questions ask you to identify similarities and differences.
Key technique: Structure your answer using explicit comparison language — "whereas," "in contrast," "both X and Y," "unlike." Avoid writing two separate descriptions and leaving the examiner to do the comparing.
| To show similarity | To show difference |
|---|---|
| Both X and Y... | Whereas X..., Y... |
| Similarly, ... | In contrast, ... |
| Like X, Y also... | Unlike X, Y... |
| In both cases, ... | However, ... |
| X and Y share... | On the other hand, ... |
Example: "Compare gravitational and electric fields."
A strong answer would compare: both follow inverse-square laws, both have field strength and potential, gravitational force is always attractive whereas electric force can be attractive or repulsive, gravitational field strength depends on mass while electric field strength depends on charge, field lines point towards masses but towards negative charges. The gravitational constant G is vastly smaller than the Coulomb constant k, meaning gravitational forces between small objects are negligible whereas electric forces between charged particles are enormous.
These questions present data, a statement, or an experimental method and ask you to assess it.
Structure:
Before writing, spend 30–60 seconds planning:
| Command word | What it requires | Common mistake |
|---|---|---|
| State / Give | Brief factual answer | Writing too much |
| Describe | Say what happens, step by step | Giving reasons (that is explaining) |
| Explain | Say why something happens, using physics principles | Only describing without giving reasons |
| Compare | State similarities AND differences explicitly | Writing two separate descriptions |
| Evaluate | Assess strengths and weaknesses, then give a judgement | Only listing positives or only listing negatives |
| Suggest | Apply physics knowledge to an unfamiliar context | Not attempting because the context is new |
| Derive / Show that | Start from known equations and reach the given result | Working backwards from the answer |
Extended response questions assess the quality of your written communication. This means:
| Vague / incorrect | Precise physics terminology |
|---|---|
| "Gets bigger" | "Increases" or "increases linearly" |
| "Goes down as it goes up" | "Is inversely proportional to" |
| "The force equation" | "Newton's second law, F = ma" |
| "Bending around corners" | "Diffraction" |
| "Energy is lost" | "Energy is dissipated as thermal energy" |
| "Making electricity" | "Electromagnetic induction" |
| "The atoms move more" | "The mean kinetic energy of the molecules increases" |
| "Heavier" | "Greater mass" |
Question: "Describe how you would investigate how the time period of a simple pendulum depends on its length." (6 marks)
Model answer:
Set up a pendulum by attaching a small, dense bob to a length of inextensible string fixed at a clamp stand. Measure the length from the pivot point to the centre of the bob using a metre ruler.
Displace the bob through a small angle (less than 10°) and release it. Use a stopwatch to time 10 complete oscillations, then divide by 10 to find the period — this reduces the percentage uncertainty in the timing measurement.
Repeat the timing three times at each length and calculate a mean period. Increase the string length in equal increments (e.g., 0.10 m) and repeat.
Plot a graph of T² against length (L). Theory predicts T = 2π√(L/g), so T² = (4π²/g)L. The graph should be a straight line through the origin with gradient 4π²/g, from which g can be determined.
Keep the mass of the bob, the amplitude of swing, and the environmental conditions constant throughout.
Extended-response questions are the place where many otherwise strong Edexcel 9PH0 candidates leak the most marks. The physics knowledge is usually in place — what falters is structure, depth, and the discipline of writing in connected prose rather than fragmented bullets. The 6-mark extended-response question is not a longer short-answer question; it is a separate genre with its own marking scheme, its own pacing, and its own preparation drills. The sections below break down how those marks are awarded, where the time goes, and the procedural habits that earn full credit reliably.
Every Edexcel 9PH0 paper carries at least one extended-response question worth 6 marks, and Papers 2 and 3 routinely carry two. These questions are signposted both by their mark value and by the demand verbs in the stem: explain, describe and explain, discuss, evaluate, compare. A 6-mark question that requires structured prose rather than a calculation is the signature pattern.
The marking is described in Edexcel materials as Quality of Extended Response (QER) — a levels-based scheme rather than a points-based one. This is the single most important distinction to internalise. On a typical 3-mark calculation question, three correct atomic facts in any arrangement will score 3 marks. On a 6-mark QER question, six unconnected correct facts may score only 3 or 4 marks because the sustained line of reasoning, terminology, and structure are themselves part of what is assessed. Two candidates can write answers containing the same factual content and receive different marks because one wrote a coherent argument and the other wrote a list.
The assessment objective mix on extended-response questions typically combines AO1 (knowledge and understanding of physics principles) with AO2 (application of that knowledge to a stated context). Some questions also draw on AO3 (analysis, interpretation, and evaluation of evidence) — these tend to be the evaluate and discuss variants, where you are asked to weigh up a method, a model, or a piece of data. A small number of extended-response questions on Paper 3 are explicitly synoptic, asking you to link two topic strands (for example, oscillations with energy, or fields with circuit theory) inside a single argument.
The structural pattern that earns full credit is consistent across topics. A Level 3 answer (worth 5–6 marks under the QER scheme) makes a sequence of distinct physics points, each anchored to a named principle, equation, or quantitative detail, and each connected to the next by an explicit logical link. The link is what distinguishes a Level 3 answer from a Level 2 one: an answer that says "the photon energy is hf. The work function is the minimum energy needed. Photoelectrons are emitted" contains three correct statements but no causal chain. An answer that says "the photon energy hf is the energy delivered to a single electron in a one-photon-one-electron interaction; if hf is greater than the work function, the excess appears as kinetic energy of the photoelectron, which is why intensity (the number of photons per second) does not change the maximum kinetic energy" contains the same physics inside a connected argument and reaches Level 3.
A 6-mark extended-response question deserves roughly 7–9 minutes of paper time. The lower bound assumes a topic you have rehearsed; the upper bound covers questions in unfamiliar contexts where you need a longer plan.
| Mark value | Target time | Realistic upper bound | Typical question type |
|---|---|---|---|
| 6 marks (QER) | 7 min | 9 min | Explain a phenomenon, compare two models, describe an experiment, evaluate a claim |
| 8 marks (QER) | 10 min | 12 min | Synoptic explanation linking two topic strands, with quantitative reasoning |
| 9–12 marks (QER, Paper 3 synoptic) | 12 min | 16 min | Multi-strand argument with embedded calculation or graph reading |
Inside a 7-minute budget, the time should be deliberately split. Aim for roughly 60–90 seconds of planning before writing a word, around 5 minutes of focused prose-writing that hits four to six distinct physics points each anchored to a principle or equation, and 30–60 seconds re-reading the question stem and the final paragraph to confirm you have answered the actual demand verb. Candidates who skip the plan typically write a single dense paragraph that scores 3 or 4 marks; candidates who plan reliably reach 5 or 6.
The plan itself is a margin sketch — four to six bullet points written next to the question, each labelled with the topic strand or principle it draws from. A typical plan for "explain how a step-up transformer increases the voltage of an alternating supply" might read: (1) primary AC produces changing flux in core; (2) iron core links flux to secondary; (3) Faraday's law: induced EMF proportional to rate of change of flux; (4) more turns on secondary → larger induced EMF; (5) ratio Vs/Vp = Ns/Np; (6) energy conservation: power roughly constant, so current decreases as voltage increases. That margin plan is the answer in skeleton form. Writing it costs 90 seconds and converts a 3-mark answer into a 5–6 mark one.
For the 8-mark synoptic extended-response questions on Paper 3, the same discipline applies but the plan needs an extra step: identify the two topic strands the question is testing before listing your physics points. A question that asks you to "explain why the maximum kinetic energy of an oscillating mass at the centre of its motion equals the elastic potential energy stored at the amplitude" spans simple harmonic motion and energy conservation. The plan must touch both strands explicitly; a candidate who answers only in the language of SHM will plateau at Level 2 even with correct physics.
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