Before using a spreadsheet graph in A-Level H2 Physics 9478 Paper 4, check which variable belongs on each axis. A graph can look straight and still give the wrong gradient if the axes are reversed. SEAB’s 2027 syllabus directory links the Paper 4 specimen, its data file and the Excel Reference Guide. Use those materials to practise the workflow for the current syllabus.
Read the instruction as “vertical quantity against horizontal quantity”. Write the expected units of the gradient before calculating it. That gives you an independent way to check whether your graph and your interpretation agree.
- Identify the requested vertical and horizontal quantities.
- Check units and any transformed data before plotting.
- Inspect one plotted point against the source table.
- Compare your gradient units with what the question asks you to determine.
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Start from the quantities in the task
If the instruction asks for force against extension, force is vertical and extension is horizontal. If the table gives extension in centimetres and your calculation needs metres, check whether to convert the column or convert the final gradient. Label what you have used so that the conversion happens once.
A transformed graph works the same way. If a task asks for time squared against length, check that the series points to the squared values. A column with the correct label and the wrong formula can still produce a chart.
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Worked example | One straight line and two gradients
Consider two idealised measurements. At an extension of 0.020 m the force is 1.0 N. At 0.050 m the force is 2.5 N. For force against extension, divide the change in force, 1.5 N, by the change in extension, 0.030 m. The gradient is 50 N/m.
If the axes are reversed, the gradient from the same two points is 0.020 m/N. It represents a different quantity. A quick units check reveals the swap even though both graphs are straight. In a practical task, use the method and data the question specifies. These two points simply demonstrate the axis check.
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CHAPTER 3 OF 4 · Back to contents
Confirm the chart against one source row
Pick one measurement pair and locate its point. Ask whether the horizontal coordinate equals the intended x value and whether the vertical coordinate equals the intended y value. Then check the axis labels and any stated units. If a chart begins to look unfamiliar, compare it with the original data before changing the scale.
After finding a gradient, write its value and units together. If the question asks you to determine a physical constant from it, check the equation that connects the two before copying the number into the answer.
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CHAPTER 4 OF 4 · Back to contents
Frequently asked questions
Can I tell that the axes are right from the shape?
Use a source row and the gradient units. Reversed axes can still produce a line with a plausible shape.
Where are the official practice files?
Find Physics 9478 in the SEAB 2027 A-Level school-candidate directory for the syllabus, specimen Paper 4 and data file. SEAB also links its Excel Reference Guide.