Core Practicals: Exam Question Types

This lesson focuses on how the 8 core practicals from the Edexcel GCSE Physics (1PH0) specification are tested in the exam. You will learn the types of questions examiners ask, the key terminology you must use correctly, and how to structure answers about experimental methods.

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How Core Practicals Are Tested

Core practical questions in the exam typically fall into six categories:

graph TD
    A["Core Practical<br/>Exam Questions"] --> B["Describe the method"]
    A --> C["Identify variables"]
    A --> D["Evaluate the method"]
    A --> E["Suggest improvements"]
    A --> F["Analyse data"]
    A --> G["Draw conclusions"]

    style A fill:#2c3e50,color:#fff
    style B fill:#2980b9,color:#fff
    style C fill:#27ae60,color:#fff
    style D fill:#e67e22,color:#fff
    style E fill:#c0392b,color:#fff
    style F fill:#8e44ad,color:#fff
    style G fill:#16a085,color:#fff

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Type 1: Describe the Method

These questions ask you to outline how to carry out an experiment. Your answer must be detailed enough that someone could follow your instructions.

How to Structure a Method Answer

1. List the equipment needed.
2. Describe the setup — draw a diagram if helpful.
3. State what you measure and how (including instruments).
4. Explain how you change the independent variable and what you keep constant.
5. State how you record and process results (table, graph, calculation).
6. Mention repeats — take at least 3 readings and calculate a mean.

Worked Example

Describe how you would investigate how the resistance of a wire depends on its length. [6 marks]

Model Answer:

Set up a circuit containing a power supply, an ammeter in series, a voltmeter in parallel with the test wire, and a length of constantan wire secured along a ruler. Use crocodile clips to connect to the wire at measured lengths.

Measure the length of the wire between the crocodile clips using the ruler. Record the ammeter and voltmeter readings. Calculate the resistance using R = V / I.

Change the length of wire by moving one crocodile clip (e.g. test lengths of 10 cm, 20 cm, 30 cm, up to 100 cm). Keep the material, diameter, and temperature of the wire the same throughout.

Repeat each measurement three times and calculate the mean resistance for each length. Plot a graph of resistance (y-axis) against length (x-axis). A straight line through the origin shows resistance is directly proportional to length.

Exam Tip: When describing a method, be specific. Do not write "measure the resistance" — write "record the ammeter and voltmeter readings and calculate resistance using R = V / I." Examiners want to see that you know HOW to measure the quantity.

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Type 2: Identify Variables

You must be able to identify the independent variable, dependent variable, and control variables for any experiment.

Term	Definition	Example (CP6 — wire length)
Independent variable	The variable you deliberately change	Length of the wire
Dependent variable	The variable you measure	Resistance (calculated from V and I)
Control variables	Variables you keep the same to make it a fair test	Material, diameter, temperature of wire

Worked Example

A student investigates how the force applied to a spring affects its extension. State the independent variable, dependent variable, and one control variable. [3 marks]

Answer:

• Independent variable: force applied (weight added to the spring)
• Dependent variable: extension of the spring
• Control variable: the same spring is used throughout (or: starting length of the spring)

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Type 3: Evaluate the Method

Evaluation questions ask you to assess the quality of an experiment — its strengths and weaknesses.

Key Questions to Ask Yourself

• Is the experiment a fair test (are control variables properly controlled)?
• Is the experiment repeatable (would you get similar results if you did it again)?
• Are the measurements accurate (close to the true value)?
• Are the measurements precise (close to each other when repeated)?
• Are there any systematic errors (consistent errors that shift all results)?
• Are there any random errors (unpredictable variations)?

Worked Example

A student measures the specific heat capacity of an aluminium block and obtains a value of 1050 J/(kg °C). The true value is 900 J/(kg °C). Evaluate the student's experiment. [4 marks]

Model Answer:

The student's value is higher than the accepted value, which suggests a systematic error. The most likely cause is energy loss to the surroundings — not all the electrical energy from the heater goes into heating the block; some is lost by conduction, convection, and radiation. This means the student overestimates the energy needed, giving a higher calculated value of c.

To improve the accuracy, the student could insulate the block to reduce energy losses, or add a thin layer of oil between the heater and the block to improve thermal contact.

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Type 4: Suggest Improvements

Improvement questions ask how to make an experiment more accurate, more precise, or more reliable.

Common Improvements and When to Suggest Them

Improvement	When to Use It
Take more repeat readings and calculate a mean	Always valid — improves reliability
Use a more precise measuring instrument	When the resolution of the instrument is poor
Insulate the apparatus	When thermal energy is lost to surroundings
Use a data logger	When human reaction time affects measurements
Work in a darkened room	For light experiments (e.g. CP8)
Keep current low / take readings quickly	When the wire/component heats up, changing resistance
Use a longer wire / spring	To get larger, more measurable extensions/changes
Use a fiducial marker	To improve consistency of reading a scale

Exam Tip: When suggesting improvements, always explain WHY the improvement would help. Do not just write "use better equipment" — state what equipment and how it addresses a specific problem.

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Type 5: Analyse Data

Data analysis questions give you results (usually in a table or graph) and ask you to identify patterns, calculate values, or identify anomalous results.

Identifying Anomalous Results

An anomalous result is a value that does not fit the overall pattern. It is usually caused by a measurement error.

How to handle anomalous results:

1. Identify them — they stand out from the pattern.
2. Exclude them from the mean calculation.
3. Repeat the measurement if possible.
4. Do NOT delete them from the table — circle or note them.

Calculating from Data

You may be asked to:

• Calculate the mean (add all values, divide by the number of values).
• Calculate the gradient of a graph (change in y / change in x, using two widely spaced points on the line of best fit).
• Read values from a graph by interpolation (within the data range) or extrapolation (beyond the data range).

Worked Example

A student records the following extension values for a spring with a force of 3 N: 6.0 cm, 5.8 cm, 12.1 cm, 6.1 cm. Calculate the mean extension, excluding any anomalous results.

Answer:

The value 12.1 cm is anomalous — it does not fit the pattern of the other results.

Mean = (6.0 + 5.8 + 6.1) / 3 = 17.9 / 3 = 6.0 cm (to 2 s.f.)

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Type 6: Draw Conclusions

Conclusion questions ask you to state what the results show, linking back to the scientific theory.

Structure of a Good Conclusion