OCR AS Physics

Revision Notes

1.2.5 Observations & Measurements

Following Written Instructions

  • Scientists always record instructions for their experiments so that they can be repeated
  • The instructions should allow an individual to successfully carry out the experiment without any additional help or input
  • It is very important to record all required details within these instructions
  • For example:
    • The aims of the investigation
    • The variables investigated
    • The apparatus used
    • The step-by-step method
  • Often students struggle to think about the theoretical implications and explanations of the practical at the same time
  • It is important to focus on these before and after the practical has been carried out to develop a solid understanding of the purpose of the experiment

Observations & Measurements

  • Making observations and recording measurements is a key skill in practical physics

Making Observations

  • Observations should be recorded using the appropriate scientific vocabulary and should be precise
  • Vague and ambiguous language, such as ‘the time wasn’t measured very accurately’, should be avoided
    • Instead, a more appropriate thing to say would be ‘using a stopwatch to measure the oscillation time of the pendulum introduced an error due to the reaction time of the experimenter’

Recording Measurements

  • Making measurements using a range of equipment is essential in physics
  • When using a digital measuring device eg. top pan balance or ammeter
    • Record all the digits shown
    • Except in the case of a digital timer, such as a stopwatch, there is no need to record to more than two decimal places
  • When using a non-digital device eg. a ruler or a measurement cylinder)
    • Record all the figures that are known
    • Where appropriate, an additional estimated figure may be allowed

Recording Experimental Activities

  • Observations and measurements should be routinely recorded in a notebook, file or electronically
    • This enables a physical copy of the completed experiments to be kept
  • These records should be made during the laboratory session and are the primary evidence of the outcomes of experiments
  • The following will need to be included:
    • A clear explanation of the measurements or observations taken
    • Analysis of the raw data through graphs or calculations
    • The conclusions drawn from the outcomes of the experiment
    • An evaluation of the experiment eg. calculating errors and/or commenting on the limitations of experimental procedures
  • The method does not necessarily need to be included unless an investigative approach is taken where the student develops part of the procedure themselves

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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