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Working as a Physicist

Resolution, random errors and systematic errors

  • 2 things to know
  • Papers 1, 2 and 3

Overview

Recall questions on the resolution of a rule, calliper and micrometer, the difference between random and systematic error, zero errors, and accuracy against precision.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Evaluation

What does an uncertainty tell you, and what is the difference between a repeatable and a reproducible result?

Evaluation

What is the difference between a random error and a systematic error?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is meant by the resolution of a measuring instrument?

    Model answer

    It is the smallest change in the quantity being measured that produces a noticeable change in the instrument reading.

  2. 2

    What is the usual resolution of a metre rule, a vernier calliper and a micrometer screw gauge?

    Model answer

    A metre rule reads to 1 mm, a vernier calliper to 0.1 mm and a micrometer screw gauge to 0.01 mm.

  3. 3

    What is the difference between a random error and a systematic error?

    Model answer

    A random error varies unpredictably in size and direction between repeats, whereas a systematic error displaces every reading by the same amount or in the same direction.

  4. 4

    How can the effect of random error on a result be reduced?

    Model answer

    Repeat the measurement several times and take the mean, since random deviations above and below the true value tend to cancel.

  5. 5

    Why does repeating a measurement fail to remove a systematic error?

    Model answer

    Every repeat is displaced in the same direction by the same amount, so the mean is displaced by that amount too.

  6. 6

    What is a zero error, and how should it be dealt with?

    Model answer

    A zero error is a non-zero reading given when the instrument should read zero, and it is corrected by subtracting that reading from every measurement taken.

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