Units and measurements revision | chapter 2 class 11 Physics revision notes blue sky ,quick revision

Units and measurements | chapter 2 class 11 Physics revision notes blue sky | all topics covered.

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This is the best revision video of class 11 Physics chapter 2 units and measurements .blue sky 

All the important topics are covered 

This video can be used in class 11 examination and competitive exams like JEE mains and advanced , neet , aims etc. 
Topics covered-- 

Physical quantity, types of physical quantities, physical units , fundamental units and derived units , system of units 

MKS , CGS , FPS , SI , choice of standard units , advantage of si 

All fundamental units , some practical units , astronomical unit , parsec , light year , AU , dimensions of physical quantities , dimensions formula , dimensions equation , quantities on the basis of dimensions , application of dimensional equation , 

1 - checking the dimensions consistency of equations 

2- derivations of formula 

3 - conversions of 1 unit system into another 
Limitations of dimensions formula , errors in measurements

Systematic errors, random error, least count error , absolute error, mean absolute error, fraction error , percentage error 

Combination of errors

Addition, subtraction , division, multiplication error 

Defination of 

Accuracy, precision , significant figures , rounding off .

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A physical quantity is a property of a material or system that can be quantified by measurement. A physical quantity can be expressed as the combination of a magnitude and a unit. For example, the physical quantity mass can be quantified as n kg where n is magnitude and kg is the unit.
The SI base units are the standard units of measurement defined by the International System of Units (SI) for the seven base quantities of what is now known as the International System of Quantities: they are notably a basic set from which all other SI units can be derived. The units and their physical quantities are the second for time, the metre for measurement of length, the kilogram for mass, the ampere for electric current, the kelvin for temperature, the mole for amount of substance, and the candela for luminous intensity. The SI base units are a fundamental part of modern metrology, and thus part of the foundation of modern science and technology.

Unit of measurement

of quantity. Any other quantity of that kind can be expressed as a multiple of the unit of measurement. For example, a length is a physical quantity.

Formulae of Dimensional 

The expressions or formulae which tell us how and which of the fundamental quantities are present in a physical quantity are known as the Dimensional Formula of the Physical Quantity. Dimensional formulae also help in deriving units from one system to another. It has many real-life applications and is a basic aspect of units and measurements.

A dimensional formula is always closed in a square bracket [ ]. Also, dimensional formulae of trigonometric, plane angle and solid angle are not defined as these quantities are dimensionless in nature.

Dimensional Formula of some physical quantities.

Example
Dimensional formula of Velocity is [M0LT-1]
Dimensional formula of Volume is [M0L3T0]
Dimensional formula of Force is [MLT-2]
Dimensional formula of Area is [M0L2T0]

Limitations of dimensions formula-- 
It cannot derive relation or formula if a physical quantity depends upon more than three factors having dimensions. It cannot derive a formula containing trigonometric function, exponential function, and logarithmic function. It cannot derive a relation having more than one part in an equation.
What are Errors in Measurement? 
An error or fault can be described as the disparity between the calculated worth and the exact worth. For instance, if the two machinists use a similar instrument for discovering the errors in measurement, it is not required that they may acquire the related outcomes. But, there will be a slight variation between both the measurements which is known as an error. In sequence, to know the idea of errors in measurement, one has to recognize the two conditions that describe the error namely measured value as well as true value. The “true value” is unfeasible to find out the accuracy of measurement by experimental means that can be defined as the standard value of a countless number of calculated values. This value can be described as the expected value of true value which can be established by taking numerous calculated values throughout experimentation.



Types of Errors in Measurement 
Systematic Errors

Gross Errors

Random Errors

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