Measurement of any physical quantity can never be exact due to many factors. Errors in the measurement are inevitable. We can define Errors or Uncertainty in the measurement as the deviation of measured values from the exact (True) values.

We cannot completely remove the errors but we can minimize the errors and get accurate measurements. One of the things that we do to make our measurement reliable is, we take many measurements and take an average of all those measured values for our final result.

Some errors that may occur in the measurements are described below:

## a. Personal Error

Performing measurements without proper knowledge of procedure and equipment may give errors in our measurement. The false setting of pieces of equipment, carelessness, faults in observation give rise to personal errors.

## b. Instrumental Error

Sometimes, the equipment we use in our measurement may be imperfect in design or may have wrong calibrations. Problems in the instrument give rise to instrumental errors. We have to adjust the measured values to make our measurement reliable during such errors.

For eg. The weighing machine shows 0.5 kg without putting any weights on it. In that case, we have to adjust our measurements by 0.5 kg to make our measurements reliable.

## c. External Cause Error

The external factors like temperature and pressure may affect our measurements unreliable. The errors due to such factors are External cause errors. We have to note down such factors and even make corrections on our working formula to make our measurements free from such errors..

## d. Imperfection Error

This error occurs due to imperfection in an experiment technique or procedure. Different experiments require different procedures to obtain a true result. Using the same technique everywhere results in an error.

## e. Precision Error/Human Error/Chance Errors

Performing measurements only once has a very good chance of having errors due to many factors. We can minimize such errors by taking multiple measurements and taking an average of such measurements to get a final result.

Experimentalists always perform multiple experiments to get multiple measurements and finally obtain the result by averaging them.

## f. Least Count Error

The least amount of quantity that can be measured by the measuring instrument is called least count (L.C) of the instrument. The least count of measuring instruments put limitations on the accuracy of the measurement.

Let’s measure the length of the same rod using different scales.

We say the length is 4 cm. It would be wrong to write the length of that rod as 4.5 cm because this ruler cannot measure the length of less than 1 cm. So least count of this scale is 1 cm. Hence, there is always an error or uncertainty of 1 cm while using this scale as a measuring instrument.

We say the length is 4.5 cm. It would be wrong to write the length of that rod as 4.57 cm because this ruler cannot measure the length of less than 1mm (or 0.1cm). So least count of this scale is 0.1 cm and hence there is always an error or uncertainty of 0.1cm while using this scale as a measuring instrument.

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