Accuracy, Precision and Error in measurements, Physics Class 11

Accuracy and Precision of measuring instruments:

Accuracy:  The closeness with which an instrument gives results to match with the true value is called accuracy.

In other words, it can be defined as the difference between the observed value and the true value. i.e.  less the difference means more accurate the measurement is.  The accuracy of a measuring instrument somehow depends upon the systematic errors.

Precision:  The degree to which an instrument will repeat the same value of measurement is called a precision.

                  It shows the difference between different observations of a measurement.

The precision of a measuring instrument depends upon the random errors. In terms of significant figures, more significant figures the instrument use to define the value, more precise the value is.

Error in measurement

Error:   The difference between true value and the measured value in measuring a physical quantity is called the error of the measurement.

For example : 

 

        If     T = true or actual value

                t  =. Measured value

          Error  =  T - t

Types of error:

There are mainly two types of error occur  in instruments :

• Systematic error

• Random error

Systematic Error :

 

Systematic errors are those errors that tend to be in one direction, either positive or negative. These errors occur due to the physical defect in the system of measurement.

There are Mainly three sources of systematic errors :

1. Instrumental errors : these errors occur due to imperfect design or calibration of the measuring instrument, zero error in the instrument, friction, resistance, etc.

2. Technique errors : If we use the technique or procedure of experiments in a wrong way then these errors occur. 

3. Personal errors : These types of errors occur due to imperfect working of a person and by the mistake in taking the observation by an observer.

 systematic errors are either positive or negative. And these types of errors can be corrected. 

Random error :

These types of error occur due to some unknown factors. It may be positive or negative or both.

Since the causes are unknown, it can not be corrected. Whereas, by taking a large number of observations, random errors can be reduced or removed.

Get notes related to

Physics Class 9 & 11 ( based on new revised syllabus )

1. Physical world

• Physical world, part -1
• Scope and excitement of Physics, part -2
• Nature of physical laws, part - 3

2. Units and Measurements

• Units and Measurements, part-1
• Length, mass and time Measurements
• Estimation or Calculation of errors
• Significant Figures and its Rules
• Dimensional Analysis

For other notes of class 9, 10, 11 and 12 Physics

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