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| Accurate Measurement |
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| No measurement is ever perfectly accurate. Even with high precision instruments some error is inevitable. |
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| There are two main types of errors: |
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Random errors occur in all measurements. They arise when observers
estimate the last figure of the reading on an instrument. These include the
noise in the room or the mechanical vibrations in the room. These are called
random, because they cannot be predicted. The best way of minimizing the
error is to take the average of many readings. |
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Systematic errors: Such mistakes are not random, but constant. They may cause an experimenter to under estimate or over estimate a reading. Systematic errors may be due to defective equipment - for instance, an incorrectly marked ruler; or they may be due to environmental factors - for instance, the weather conditions on a particular day. While recording time using a stop-watch, your reaction time in starting or stopping the stop-watch will certainly vary at times significantly if you are tired or distracted. At times the variation will be more than a few hundredth of a second. |
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| Percentage Error |
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| While reading the length of a simple pendulum or the length of a resistance wire or while finding the weight of a body using spring balance, mass by a beam balance etc., we are likely to make mistakes. The percentage error can be calculated by using the formula. |
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Percentage error  |
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| For example, if the length of an object (100cm long) is measured as 99.8 cm, then |
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% error  |
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Measurement and Experimentation
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