How to answer A Level Physics questions about practical experiments

Students are often unsure of how to answer questions about practical work. This is a brief guide to the main points that should be covered in order to adequately describe the procedure to be followed. The categories included below are based on various exam markschemes I have encountered over ten years teaching physics. They are not intended to be a specific formula for any particular exam specification. Students should always read the question carefully and address any specific points raised.

 

Try to include most or all of the following points. This looks like a lot of work but most of these can be covered very briefly.

  • EQUIPMENT

o Labelled diagram

o List any equipment not shown in diagram

  • METHOD

o What measurements do you need to take?

  • The actual physical measurements (i.e. diameter NOT cross-sectional area)

o What equipment will you use to take each measurement?

  • Mention it, even if it’s something as obvious as using a ruler to measure length.

o Range and values

  • E.g. “Load spring with 100g masses in 10 stages up to a maximum of 1kg.”

o Repeats

  • Take 3 repeats and calculate mean if possible.
  • For Hooke’s Law/Young’s Modulus experiments, repeat readings for loading and unloading.
  • For small readings, measure in large multiples to reduce %-uncertainty (e.g. record time taken for 10 or 20 pendulum swings and then divide by 10 or 20 to calculate time period)

o What calculations do you need to do?

  • (e.g. halve diameter to find radius then A =πr² for cross-sectional area)
  • RESULTS

o This is nearly always a GRAPHICAL method, not just subbing one set of results into an equation.

o What will you put on each axis?

  • Something you measured (e.g. current) or something you calculated from your measurements (e.g. resistance)

o What do you need to read from the graph?

  • Gradient? (nearly always!)
  • Intercept? (occasionally!)
  • Something else, like checking for a straight line through the origin (indicating proportionality)

o Any further calculations?

  • E.g. Is your gradient the final “answer” or do you need to multiply/divide by a constant to get the value you’re looking for?
  • HEALTH & SAFETY

o This doesn’t seem to be on the mark scheme so much these days but if there’s something obvious like wearing eye protection then mention it – can’t hurt!