Using Appropriate Instruments & Techniques (OCR A Level Physics)

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Using Appropriate Instruments & Techniques

  • Being familiar with how to use a wide range of experimental and practical instruments is essential for both practicals and written exam questions
  • Scientific instruments can be digital or analogue

Analogue

  • Analogue scientific instruments transfer information through electric pulses of varying amplitude
    • This means they cannot be read easily by a computer

  • Analogue instruments are cheaper but they have lower accuracy and resolution
  • They are also more sensitive, which can make it difficult to read fluctuating values
  • An analogue display normally involves a pointer which indicates a value depending on its position or angle on the scale

    Analogue display, downloadable AS & A Level Physics revision notes

    Analogue meter

  • The measurements taken on this analogue ammeter are restricted over a range e.g. 0 - 10 A and a resolution of 1 A
  • Analogue meters are subject to zero errors
    • This means the marker must be double-checked before each reading. If it is not at zero, then the value but be subtracted from all the measurements

  • They are also subject to parallax error
    • Always read the meter from a position directly perpendicular to the scale

  • A potentiometer is an example of a sensitive analogue meter

Digital

  • Digital scientific instruments translate information into binary (0 or 1) format which can then be read and analysed by a computer
  • They are more expensive but have greater accuracy and resolution than analogue
  • Digital displays show the measured values as digits
  • They’re easy to use because they give a specific value and are capable of displaying more precise values

Digital display, downloadable AS & A Level Physics revision notes

Digital meter

  • The measurements taken on this digital ammeter have a much wider range and a resolution of 0.01 A
  • Digital meters are also subject to zero error
    • Make sure the reading is zero before starting an experiment, or subtract the “zero” value from the end results

  • Most digital meters have an auto-range function, this means it can show very low or very high values depending on the readings
    • This saves time selecting an instrument with the correct range and precision for your experiment

  • A digital multi-meter is an example of a digital meter

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.