Edexcel International A Level Physics

Revision Notes

3.4 Measuring Variables

Measuring Variables

  • When measuring a variable in an experiment, it is important to use the most appropriate instrument and measuring technique to achieve the most accurate value for that measurement
  • A list of the common apparatus and their purpose is shown in the table below:

Apparatus and Their Purpose Table

Experimental Instrument Purpose Example
Metre ruler To measure the length of an object of a length between 1 cm - 1 m Length of a wire
Vernier Calipers To measure short lengths between 0.1 mm - 1 cm Extension of a wire
Micrometer Screw Gauge To measure very short lengths between 0.01 mm – 0.1 mm Diameter of a wire
Top-pan Balance To measure the mass of an object Weight of a block
Protractor To measure angles Measuring angle of refraction of a beam of light
Stopwatch To measure time Time taken for an oscillation
Thermometer To measure temperature Temperature increase for specific heat capacity of a material
Voltmeter To measure potential difference Potential difference across a bulb
Ammeter To measure current Current through a bulb
Oscilloscope To display waves and measure their frequencies Frequency of a signal
Laser To provide a monochromatic, coherent source of light Investing the interference of light

  • The key factor associated with choosing the appropriate instrument is its resolution
    • If the resolution of an instrument is too big, then it won't be able to measure small measurements

Exam Tip

When planning experiments, make sure to really think about which instrument you need to measure the length of something. A rough rule could be:

  • Length will be between a few cm – 1 cm, use a ruler
  • Length will be between 0.1 mm – few cm, use a vernier caliper
  • Length will be between 0.01 mm – 0.1 mm, use a micrometer

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