Pearson IGCSE Physics Practical 1: Planning, Variables and Fair Tests

Study guide

Plan valid Pearson International GCSE Physics investigations with measurable variables, controls and repeats.

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A physics plan must define a measurable relationship and keep all competing physical effects controlled.

Pearson assesses practical understanding within the written International GCSE Physics papers. A planning answer must therefore be more than a list of apparatus: it should tell another student what to change, what to measure, what to keep constant, how to collect enough evidence and how to decide whether the evidence supports the proposed relationship.

A physics investigation workflow from defining the relationship to checking whether the evidence can answer the question.

Planning checklist

  • State the independent-variable range, intervals and method of adjustment.
  • Define the dependent variable and the instrument used to measure it.
  • Control geometry, material, temperature, supply voltage or starting conditions as relevant.
  • Use repeated readings or repeated timing over many cycles to reduce random uncertainty.
  • Describe how the apparatus is aligned, zeroed and kept stable.
  • Match hazards such as hot objects, radiation or falling masses to specific controls.

Define what will actually be measured

Start by turning the question into a relationship between two measurable quantities. In How does the force on a spring affect its extension?, force is the independent variable. Extension is the dependent variable, but it must be operationally defined as the stretched length minus the original unloaded length. This distinction prevents a common error: recording the total spring length and calling it extension.

Write the independent-variable range and interval before writing the method. Five or more well-spaced values usually reveal a trend more convincingly than two extreme readings. The range must also suit the apparatus and physical model. A spring must remain below its limit of proportionality; a current must remain below the component rating; a temperature range must be safe and measurable. A pilot reading can reveal whether the chosen range produces changes larger than the instrument resolution.

The dependent variable must be paired with an instrument and a reading procedure. Measure time is incomplete. State whether a stopwatch, light gate, data logger or oscilloscope is used, what event starts and stops the measurement, and whether timing several cycles will reduce percentage uncertainty. Select an instrument with a suitable range and resolution. A metre rule marked every millimetre cannot justify readings to 0.01 mm \pu{0.01 mm}

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Sources

  1. Pearson International GCSE Physics 4PH1 specification