## Pradeep Kshetrapal is teaching live on Unacademy Plus

PHYSICS CLASS XI (+1/ Chapter 2 Units and Measurement Lecture no XI-2-B-1 rors in measurement Physics by Pradeep Kshetrapal

Error is the unavoidable part of th measurement. Whatever good instruments we use and care we take there is always an error in measurement. The "measured value" may be different then 0%"true value" Ov Physics by Pradeep Kshetrapal

There is limit to time and cost involved in measurement, hence we have to tolerate the error to some extent. Therefore the error in measurement is also known as "tolerance" in measurement. May be this difference is very-very small and negligible, but there is always some olerance in any measurement we do 9 3 Physics by Pradeep Kshetrapal

Considering cause and result, the errors are divided broadly in to two classes 1.Systematic errors: These are the errors which take place due to errors withSystem components of measurement process. And these system components are (ayInstruments used (biformula and principle used, and person who is doing the measurement. Physics by Pradeep Kshetrapal

(a) Errors in Instrument: Calibration may not be accur Zero error at starting point may be there; wear and tear loose contacts; and leasticount not small enough. Physics by Pradeep Kshetrapal

(b) Errors in formula and process du The principle taken itself is not precise enough. The formula has neglected many quantities hich actually matter. Ov Physics by Pradeep Kshetrapal

(c) Personal errors : These are due to person who is performing the measurement. It is due to his carelessness, wrong method of taking observation and any other personal mistake which brings in error Ov Physics by Pradeep Kshetrapal

The systematic errors are generally repeated in the same manner in every observation, hence these are called uni-directional. Like; if a defective scalevneasures 0.5 kg less, then it will do so in each observation. Therefor it is possible to measure and correct systematic errors during calculations. Physics by Pradeep Kshetrapal

Random Errors When we take different measurements the end results do not match due to unknown reasons then these errors are Random errors The cause of these errors is not known to us ana therefore we can not correct it by calculations. Physics by Pradeep Kshetrapal

Because cause of the random error is not known, these may be positive or negative i.e. multi-directional. Taking advantage of this probability, we can eliminate this error by, taking a large number of observations and then taking average of the same. With principle ofprobability we assume that positivaand negative errors cancel out and the error is eliminated. Physics by Pradeep Kshetrapal

Last digit error For any given number the last non-zero digit is uncertain and digits before that (on lef are certain. The unit value of last digit is the error. Example: In 2345 meter last digit is 5 at unitaryplace, hence 1 meter is error. Physics by Pradeep Kshetrapal

du 019 In the next lesson we will study about calculation of different types of errors. Ov Thank You Physics by Pradeep Kshetrapal