Question

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Answer 1

Answer:

Explanation:

An instrument is accurate when it gives the correct value of the quantity being measured

e. g. if we perform an experiment to determine the density of mercury and we get a value of 8.5 − instead of − the inaccurate answer could be due to the balance or the measuring cylinder being inaccurate (once the experiment has not committed any error)

Select the instruments you would use to measure the following. State why you have chosen each instrument and give the range of measurements possible with the instrument and its sensitivity.

The thickness of a human hair

The diameter of a table tennis ball

The area of a window pane

The inside diameter or bore of a water pipe

The diameter of a bolt when deciding the size of the hole to drill

The volume of liquid in a wine bottle

ERRORS

13 Errors are normally classified in three categories: systematic errors, random errors, and blunders.

A final source of error, called a blunder, is an outright mistake. A person may record a wrong value, misread a scale, forget a digit when reading a scale or recording a measurement, or make a similar blunder. These blunder should stick out like sore thumbs if we make multiple measurements or if one person checks the work of another. Blunders should not be included in the analysis of data.

14 Systematic Errors

Systematic errors are due to identified causes and can, in principle, be eliminated. Errors of this type result in measured values that are consistently too high or consistently too low. Systematic errors may be of four kinds:

Instrumental. For example, a poorly calibrated instrument such as a thermometer that reads 102 oC when immersed in boiling water and 2 oC when immersed in ice water at atmospheric pressure. Such a thermometer would result in measured values that are consistently too high.

Observational. For example, parallax in reading a meter scale.

15 Systematic Errors continued

Environmental.

Theoretical.

16 Random Errors

Random errors are positive and negative fluctuations that cause about one-half of the measurements to be too high and one-half to be too low. Sources of random errors cannot always be identified. Possible sources of random errors are as follows:

1. Observational. For example, errors in judgment of an observer when reading the scale of a measuring device to the smallest division.

17 Environmental. For example, unpredictable fluctuations in line voltage, temperature, or mechanical vibrations of equipment.

Random errors, unlike systematic errors, can often be quantified by statistical analysis, therefore, the effects of random errors on the quantity or physical law under investigation can often be determined.

18 An example fitting to distinguish between systematic and random errors is suppose that you use a stop watch to measure the time required for ten oscillations of a pendulum. One source of error will be your reaction time in starting and stopping the watch. During one measurement you may start early and stop late; on the next you may reverse these errors. These are random errors if both situations are equally likely.

Repeated measurements produce a series of times that are all slightly different. They vary in random vary about an average value.

If a systematic error is also included for example, your stop watch is not starting from zero, then your measurements will vary, not about the average value, but about a displaced value.  

19 Blunders

A final source of error, called a blunder, is an outright mistake. A person may record a wrong value, misread a scale, forget a digit when reading a scale or recording a measurement, or make a similar blunder. These blunder should stick out like sore thumbs if we make multiple measurements or if one person checks the work of another. Blunders should not be included in the analysis of data.

20 Click on the links to watch the tutorials!

Using the Instruments

The vernier caliper

The micrometer

The triple beam balance

Click on the links to watch the tutorials!

Download ppt "Sensitivity, Accuracy And Range Of An Instrument"