Core Practical 3: Investigating Young Modulus (Edexcel International A Level Physics)

Revision Note

Test Yourself
Lindsay Gilmour



Core Practical 5: Investigating Young Modulus of a Material

  • To measure the Young Modulus of a metal in the form of a wire requires a clamped horizontal wire over a pulley (or vertical wire attached to the ceiling with a mass attached) as shown in the diagram below


Apparatus, downloadable AS & A Level Physics revision notes

  • A reference marker is needed on the wire. This is used to accurately measure the extension with the applied load
  • The independent variable is the load
  • The dependent variable is the extension


  1. Measure the original length of the wire using a metre ruler and mark this reference point with tape
  2. Measure the diameter of the wire with micrometer screw gauge or digital calipers
  3. Measure or record the mass or weight used for the extension e.g. 300 g
  4. Record initial reading on the ruler where the reference point is
  5. Add mass and record the new scale reading from the metre ruler
  6. Record final reading from the new position of the reference point on the ruler
  7. Add another mass and repeat method


Reducing Uncertainty

  • To reduce the uncertainty in the final answer, take the following precautions when measuring
    • Take pairs of readings of the diameter right angles to each other, to ensure the wire is circular
    • Six to ten readings altogether is enough to get an average value
    • Remove the load and check the wire returns to the original limit after each reading. A little 'creep' is acceptable but a large amount indicates that the elastic limit has been exceeded
    • Take several readings with different loads and find average
    • Use a Vernier scale to measure the extension of the wire

Measurements to Determine the Young Modulus

1. Determine extension x from final and initial readings

Example table of results:

Table of results, downloadable AS & A Level Physics revision notes

Table with additional data

Table with additional data, downloadable AS & A Level Physics revision notes

2. Plot a graph of force against extension and draw line of best fit

3. Determine gradient of the force v extension graph

Force extension graph results, downloadable AS & A Level Physics revision notes

4. Calculate cross-sectional area from:

Cross sectional area equation, downloadable AS & A Level Physics revision notes


5. Calculate the Young modulus from:

Young's modulus using graph, downloadable AS & A Level Physics revision notes

Safety Considerations

  • Safety glasses should be worn in case of the wire snapping
  • Protect feet and the floor from falling weights by cushioning the area underneath the weights

Exam Tip

Although every care should be taken to make the experiment as reliable as possible, you will be expected to suggest improvements in producing more accurate and reliable results

Good examples of improvements in any experiment are:

  • Take repeat readings and take an average to improve accuracy
  • Measure longer distances, such as using a longer length of wire, to reduce percentage error

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.

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