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The Edexcel A-Level Physics specification includes 16 core practical experiments. While you will not perform these experiments in the exam, Paper 3 in particular tests your understanding of practical skills through written questions. These questions can appear in any part of the paper and are worth significant marks.
You should be familiar with the apparatus, method, and analysis for each core practical. The key ones include:
| Core Practical | Topic | What you determine |
|---|---|---|
| CP1 | Mechanics | Acceleration of a freely falling object |
| CP2 | Waves | Frequency of stationary waves on a string |
| CP3 | Circuits | Electrical resistivity of a material |
| CP4 | Circuits | EMF and internal resistance of a cell |
| CP5 | Materials | Force–extension graph for a material |
| CP6 | Materials | Young's modulus of a material |
| CP7 | Waves | Speed of sound using a two-beam oscilloscope |
| CP8 | Waves | Wavelength of light using a diffraction grating |
| CP9 | Capacitors | Charge and discharge of a capacitor |
| CP10 | Fields | Force on a current-carrying conductor |
| CP11 | Waves | Resonant frequencies of vibrating strips |
| CP12 | Thermodynamics | Boyle's law: pressure–volume relationship |
| CP13 | Thermodynamics | Pressure law: pressure–temperature relationship |
| CP14 | Thermodynamics | Specific heat capacity of a material |
| CP15 | Nuclear | Half-life using a simulation or protactinium generator |
| CP16 | Waves/Fields | Inverse-square law for light intensity |
When asked to describe an experimental procedure, you should include:
graph TD
A["Describing a Procedure"] --> B["Name SPECIFIC apparatus"]
B --> C["Describe setup and arrangement"]
C --> D["State IV, DV, and controls"]
D --> E["Describe measurement technique"]
E --> F["State range and increments of IV"]
F --> G["State repeats and mean"]
G --> H["Describe analysis method"]
H --> I["State safety precautions"]
I --> J{"Does question ask\nfor a graph?"}
J -->|Yes| K["State axes, expected shape,\nand what gradient gives"]
J -->|No| L["Still mention how you\nwould process data"]
Every experiment involves three types of variable:
Example (CP6 — Young's modulus):
Being able to identify these three types of variable is a fundamental skill that appears in almost every practical question.
Uncertainty quantifies the doubt in a measurement. The key calculations are:
For a single measurement, the absolute uncertainty is typically ± half the smallest division of the measuring instrument.
| Instrument | Typical resolution | Absolute uncertainty | Best use |
|---|---|---|---|
| Ruler | 1 mm | ± 0.5 mm | Lengths > 10 cm |
| Vernier caliper | 0.1 mm | ± 0.05 mm | Small lengths, diameters |
| Micrometer | 0.01 mm | ± 0.005 mm | Wire diameters |
| Stopwatch | 0.01 s | ± 0.01 s (but reaction time ~0.2 s dominates) | Time intervals |
| Digital voltmeter | 0.01 V | ± 0.01 V | Potential difference |
| Digital ammeter | 0.01 A | ± 0.01 A | Current |
| Protractor | 1° | ± 0.5° | Angles |
| Thermometer | 1°C | ± 0.5°C | Temperature |
Percentage uncertainty = (absolute uncertainty / measured value) × 100%
Example: A wire length is measured as 1.250 m ± 0.001 m. Percentage uncertainty = (0.001 / 1.250) × 100% = 0.08%
Example: If v = 2πr/T, percentage uncertainty in v = percentage uncertainty in r + percentage uncertainty in T.
If the formula involves r², the percentage uncertainty in r² = 2 × percentage uncertainty in r.
A student calculates the resistivity of a wire using ρ = RA/L where:
Total percentage uncertainty in ρ = 2% + 6% + 0.5% = 8.5%
The dominant uncertainty comes from the diameter measurement because it is squared. This is a common exam question: "Which measurement contributes most to the uncertainty?"
Systematic errors shift all measurements in the same direction by a similar amount. They cannot be reduced by taking more readings.
Examples in physics practicals:
Random errors cause measurements to scatter around the true value. They can be reduced by taking repeat readings and calculating a mean.
Examples:
When asked to suggest improvements to an experiment, think about:
| Strategy | Example improvement | What it reduces |
|---|---|---|
| More repeats | Take 5 readings at each value and calculate mean | Random error |
| Better instrument | Use micrometer instead of vernier caliper for wire diameter | Random error + resolution |
| Data logging | Use light gate and data logger instead of stopwatch | Random error (removes reaction time) |
| Larger range | Measure over a wider range of the IV | Reduces % uncertainty in gradient |
| Eliminate systematic error | Calibrate instruments, account for background radiation | Systematic error |
| Reduce heat loss | Insulate the calorimeter with lagging | Systematic error |
| Use a comparison | Use a comparison wire to account for thermal expansion | Systematic error |
Never write "be more careful" or "avoid human error" — these are too vague to earn marks. Every improvement must be specific and actionable.
These terms have specific meanings in physics:
A set of measurements can be precise but inaccurate (all close together but far from the true value — a systematic error) or accurate but imprecise (scattered around the true value — random errors but no systematic shift).
The goal is both: accurate and precise measurements, achieved by calibrating instruments (for accuracy) and taking repeats (for precision).
A very common Paper 3 question follows this pattern:
For example: "The diameter has the largest percentage uncertainty (3%) which is doubled to 6% because it is squared in the area calculation. To reduce this, use a micrometer screw gauge instead of vernier calipers, and measure the diameter at multiple points along the wire to obtain a reliable mean."
Practical-based questions are the section of the Edexcel 9PH0 papers where strong theoretical candidates routinely under-perform. The physics is rarely the limiting factor — what fails is the language of experimental design, the discipline of variables and uncertainties, and the recognition that "describe how you would investigate..." is a structured genre with a fixed mark-scheme template, not an open prompt. Paper 3 is built around this skill, and the Practical Endorsement woven through the two-year course is the rehearsal ground for it. The sections below break down how those marks are earned, where the time goes, and the procedural habits that turn a list of apparatus into a Level-3 method.
The Edexcel 9PH0 specification builds the practical assessment around 16 Core Practicals (CPs) distributed across the eight content topics. Paper 3 (9PH0/03) is the dedicated General and Practical Principles paper, two hours and 120 marks, and although it can examine any topic from across the specification, the practical-skills questions on Paper 3 draw heavily and recognisably from these 16 named experiments. The reasoning is simple: candidates have either performed the CP themselves under the Practical Endorsement, or they have studied a written version of it, so the CP list is the common experimental vocabulary the paper assumes. Papers 1 and 2 also embed shorter practical-skills items, but Paper 3 is where the longer descriptive and evaluative questions live.
Alongside the written paper, the Practical Endorsement is reported separately as a "pass" or "not classified" judgement and does not contribute to the numerical grade. It is, however, assessed against the Common Practical Assessment Criteria (CPAC) — five strands covering the safe and skilful following of methods, the application of investigative approaches, the safe and ethical use of apparatus, the keeping of accurate records, and the use of relevant scientific terminology. The CPAC criteria are not directly examined as such in the written papers, but the practical-skills questions on Paper 3 are written to reward exactly the dispositions CPAC describes: identifying variables cleanly, planning a repeatable method, recording readings with appropriate precision, evaluating sources of uncertainty, and drawing reasoned conclusions from data.
The procedural toolkit that recurs across the 16 CPs is narrower than the topic spread suggests. Calorimetry — measuring energy transfer using a known mass of water, an immersion heater, and a temperature-time graph or final-temperature reading — appears in CP10 (specific heat capacity). Oscilloscope use — calibrating timebase and Y-gain, reading peak voltage, period, and frequency from a trace — is the measurement spine of CP11 and CP12 (frequency of an oscillator, damped oscillations). Current-voltage characteristic measurement, with a variable resistor sweeping the supply and a voltmeter and ammeter recording the corresponding values, is the core of CP6 (resistivity), CP7 (EMF and internal resistance), and CP8 (IV characteristics of a filament lamp, diode, or thermistor). Falling-ball viscometry — releasing a sphere through a tall cylinder of liquid and timing it past two reference marks once terminal velocity is reached — is CP4. Pendulum SHM — timing a known number of oscillations with a fiducial marker, then using T=2πL/g — is CP9. These five procedures alone account for a large share of the procedural language Paper 3 rewards.
A practical-skills question on Paper 3 is recognisable from several signals. The stem usually opens with describe how you would investigate, plan an experiment to determine, the student set up the apparatus shown, or the table shows results obtained from. The mark allocation is typically 4–6 marks for a method, 2–4 marks for variables and controls, 2–4 marks for an uncertainty calculation or graph-reading task, and 2–3 marks for an evaluation or improvement. These can easily run to 12–18 marks of practical content on a single paper.
Paper 3 is 120 marks over 120 minutes, which gives a clean one-minute-per-mark anchor, identical to the rule that governs Papers 1 and 2 within their slightly tighter envelope. Practical-skills questions tend to sit in the 4–10 mark band, with occasional longer items folded into a multi-part question worth 12 or more marks. The table below maps mark value to a target time for the practical-skills genre specifically.
| Mark value | Target time | Realistic upper bound | Typical practical-skills task |
|---|---|---|---|
| 2 marks | 2 min | 3 min | Identify the independent or dependent variable; state one control variable |
| 3 marks | 3 min | 4 min | Calculate a percentage uncertainty; identify the largest source of uncertainty |
| 4 marks | 4 min | 5 min | Suggest two improvements with justifications; describe one stage of a method |
| 6 marks | 6 min | 8 min | Describe a full investigation: variables, apparatus, method outline, analysis |
| 8 marks | 8 min | 10 min | Plan an investigation in full; or evaluate a given experimental design at length |
| 10 marks | 10 min | 13 min | Synoptic practical question combining method, calculation, and graph analysis |
Within a 6-minute method question the time should be deliberately split: roughly 60 seconds of planning (independent variable, dependent variable, two or three controls, apparatus), then around 4 minutes of focused prose on measurement procedure, repeats, and analysis route, then 30–60 seconds re-reading the stem. Candidates who skip the plan typically write a single dense paragraph that conflates apparatus with method and scores 3 or 4 marks; candidates who plan reliably reach 5 or 6.
For shorter uncertainty-calculation items the budget is dominated by arithmetic discipline. A 3-mark percentage-uncertainty calculation should take 3 minutes: 30 seconds to identify the measurement and instrument resolution, 90 seconds to compute the percentage uncertainty (multiplying by the appropriate power where the measurement is squared or cubed in a derived quantity), and 60 seconds to write the final value with units and an appropriate number of significant figures.
A small number of CPs and procedural patterns account for most of the practical-skills marks. Drilling these specifically is far more efficient than general practical revision.
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