Range of Measurements (Edexcel International A Level Physics)
Revision Note
Range of Measurements
When recording data from an experiment, it is important to take a good range of readings
This is between 5 – 10 values, with a step of 1, 2, 5 or a multiple of 10
Example table of results with a good range
In the diagram, there is a good range of 8 values between 0.25 – 2.00 m
A wide range of readings gives an idea of how well the average represents the data
When considering the range of readings, think about the limitations of the instrument used to measure the independent variable
An example of this is the range of the measuring device:
A maximum value of the range of 5 m when using a ruler wouldn't be ideal, because a ruler is normally 1 m long. This could become difficult to measure introducing many errors into the readings
The smallest division on a ruler is 1 mm, therefore, the smallest reading should be greater than this (e.g. not 0.1 mm)
Another example is the limitations of the apparatus used:
When measuring the extension of a spring, a large load is avoided in order for the spring not to extend past its elastic limit
Too high voltages and currents could damage the circuit as it heats up, so the highest value in the range required must be well below the limit of any components in the circuit in order for them not to fuse or set on fire
A range of readings is important to see whether the experiment holds true for all values, or, if there is a different pattern in results after a certain value
Imagine investing the variation of current and potential difference for a semiconductor diode
If a reading of potential difference were only taken up to a value of 0. 5 V, the graph would look like a horizontal line
If they were taken up to 3 V, the steep increase in current can be seen by an almost vertical straight line
Had a larger range not been taken, the full pattern of the current and potential difference in the diode wouldn't have been seen
In general, the more readings the better, and the wider range the better
However, there is only so much time set out to complete the experiment
A wider range of measurements shows a different pattern
Examiner Tips and Tricks
It is important that the difference between each reading in a range is equal (e.g. 1, 2, 3, 4 and not 1, 2 , 5, 6 ) and that the difference between each value is 1, 2, 5 or a multiple of 10 (avoid something like 0.3, 0.6, 0.9)
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