Errors and Types of Errors – Inter Physics – Error: The result of every measurement by any measuring instrument contains some uncertainty. This uncertainty in measurement is called error.
Error = True value – Measured value
True value means, standard value free of errors. Errors are broadly classified into 3 types :
i) Systematic errors
ii) Random errors
iii) Gross errors
The errors due to a definite cause and which follow a particular rule are called systematic errors. They always occur in one direction (either +ve or -ve )
Systematic errors with a constant magnitude are called constant errors.
The constant arised due to imperfect design, zero error in the instrument or any other such defects. These are also called instrumental errors.
Errors and Types of Errors – Inter Physics, Inter 1st year physics Errors and Types of Errors , error correction, error correction, measurement errors
Example for the error due to improper designing and construction.
If a screw gauge has a zero error of -4 head scale divisions, then every reading will be 0.004cm less than the true value.
The error arised due to external conditions like changes in environment, changes in temperature, pressure, humidity etc.
Ex: Due to rise in temperature, a scale gets expanded and this results in error in measurement of length.
Imperfection in Experimental
technique or Procedure: The error due to experimental arrangement, procedure followed and experimental technique is called imperfection error.
Ex: In calorimetric experiments, the loss of heat due to radiation, the effect on weighing due to buoyancy of air cannot be avoided.
Personal errors or observational errors:
These are entirely due to the personal peculiarities of the experimenter. Individual bias, lack of proper setting of the apparatus, carelessness in taking observations (without taking the required necessary precautions.) etc. are the causes for these type of errors. A person may be habituated to hold his eyes (head) always a bit too far to the right (or left) while taking the reading with a scale. This will give rise to parallax error.
If a person keeps his eye-level below the level of mercury in a barometer all the time, his readings will have systematic error.
These errors can be minimised by obtaining several readings carefully and then taking their arithmetic mean.. probable error
Ex: Parallax error
Errors and Types of Errors – Inter Physics,
Inter 1st year physics Errors and Types of Errors , error correction, error correction, measurement errors
They are due to uncontrolled disturbances which influence the physical quantity and the instrument. these errors are estimated by statistical methods.
1.Random no. of observations error
Ex-:The errors due to line voltage changes and backlash error. Backlash errors are due to screw and nut.
The cause for gross errors are improper recording, neglecting the sources of the error, reading the instrument incorrectly, sheer carelessness
Ex: In a tangent galvanometer experiment, the coil is to be placed exactly in the magnetic meridian and care should be taken to see that no any other magnetic material is present in the vicinity.
– No correction can be applied to these gross errors.
– When the errors are minimized, the accuracy increases. The systematic errors can be estimated and observations can be corrected.
– Random errors are compensating type. A physical quantity is measured number of times and these values lie on either side of mean value. These errors are estimated by statistical methods and accuracy is achieved.
– Personal errors like parallax error can be avoided by taking proper care.
– The instrumental errors are avoided by calibrating the instrument with a standard reference and by applying proper corrections.