LESSON PLAN

Prepared By PALLABI GOGOI SIBSAGAR POLYTECHNIC, Department Of Electrical SUBJECT NAME: ELECTRICAL DEMOW Engineering MEASUREMENT AND MEASURING INSTRUMENTS I ( EMMI- I) DATE:5.04.2020

SUBJECT CODE: EL- 403

SEMESTER: 4th SEMESTER CHAPTER 1: UNITS, DIMENSIONS AND STANDARDS 1st hour Basics of Physical Quantities ❖ What do you mean by physical quantities? All those quantities that can be measured directly or indirectly is called a physical quantity. ❖ Name some physical quantities Mass, Length, Time, Temperature, etc ❖ Why are physical quantities so important? Give me your opinions UNITS, DIFFERENT TYPES OF UNITS

➢ Define unit The standard measure of each kind of physical quantity is called a unit. Examples- kilogram,metre,second,kelvin, etc.

➢ Define absolute unit An absolute system of unit is defined as a system in which the various units are expressed in terms of small number of fundamental units.

DIFFERENT TYPES OF UNIT

▪ Fundamental units ▪ Derived units 2nd hour ▪ Define Fundamental units- The units whose value can be measured without the help of any other physical quantities are called fundamental units. Examples- Metre, Second, Kilogram( Units of length,time and mass respectively) .

▪ Define Derived units- The units which are expressed with the help of one or more fundamental units are called derived units. Examples- m3, m/s , m/s2 ( Units of volume, velocity and acceleration respectively).

DIFFERENT SYSTEMS OF UNIT • S.I system • C.G.S system • M.K.S system • R.M.K.S system • R.M.K.S.A system S.I system of unit The eleventh general conference of weights and measures which met in October,1960 recommended a unified systematically constituted, coherent system of fundamental, supplementary and derived units for international use. This system is called international system of units and designated as S.I system of unit. It consists of seven base units , two supplementary units and twenty seven derived units.

BASE QUANTITIES OF S.I SYSTEM OF UNIT Quantities Units Symbols LENGTH Metre m MASS Kilogram kg TIME Seconds s TEMPERATURE Kelvin K ELECTRIC CURRENT Ampere A LUMINOUS INTENSITY Candela cd

AMOUNT OF SUBSTANCE Mole mol SUPPLEMENTARY QUANTITIES OF S.I SYSTEM OF UNITS 3rd hour NAME OF QUANTITY NAME OF UNIT SYMBOL

Plane angle Radian rad

Solid angle Steradian sr C.G.S SYSTEM OF UNITS

Till now the most commonly used units in electrical work are CGS units. These quantities involve the use of a fourth quantity in addition to the units of length ,mass and time. Either electrostatics or electromagnetism are used for defining CGS units for electrical work.

DIFFERENT TYPES OF C.G.S UNITS

❑ Electromagnetic units ❑ Electrostatic units ▪ Electromagnetic units- Units based on electromagnetic effects are known as electromagnetic units or e.m units and the system is known as electromagnetic system of units or e.m.u system(µ). It includes units of four quantities; permeability of the medium and units of length,mass and time. ▪ Electrostatic units- Units based on electrostatic effects are known as electrostatic units or e.s units and the system is known as electromagnetic system of units or e.s.u system(Ɛ). It includes units of four quantities; permittivity of the medium and units of length,mass and time.

M.K.S SYSTEM OF UNITS The M.K.S system of units is a physical system of units that expresses any given measurement using fundamental units of metre, kilogram and second.

R.M.K.S SYSTEM OF UNITS In 1901,professor Giorgi introduced the MKS system where in addition to the above three quantities a fourth quantity is introduced which is the permeability and is given by µ=µ0× µ푟 where µ0 is the permeability of free space and µ푟 is the relative permeability. Therefore, MKS unit of permeability= 107× CGS unit of permeability. R.M.K.S.A SYSTEM OF UNITS 4th hour The M.K.S in its rationalised form utilizes four fundamental units. These are metre, kilogram, second and ampere. The use of fourth fundamental unit has been recommended by Electro-technical commission in July 1950. DIMENSIONAL ANALYSIS ➢ On what grounds units are related to dimensions? ➢ How the units are converted in Mass, Length and Time(MLT) ? Conversions of some derived physical quantities length velocity 1) Velocity= 2) Acceleration= time time [L] [LT−1] [v]= =[LT−1] [v]= =[LT−2] [T] [T] 3)Force= mass×acceleration 4) Work= force×distance [F]= [M]× [LT−1] =[MLT−2] [W]= [MLT−2][L]= [ML2T−2]

Find the dimensions of the following- 1. Power 2. Energy 3. Momentum 4. Torque 5. Stiffness 6. Surface tension 7. Dynamic viscosity Relation between Electromagnetic ( e m) and Electrostatic ( e s) units and showing the derivation (6th hour)

Some dimensions of physical quantities in esu and evaluation of those. 7th hour Some dimensions of physical quantities in esu and evaluation of those. Some dimensions of physical quantities in emu and evaluation of those. (8th hour) Some dimensions of physical quantities in esu and evaluation of those. 9th hour

10th hour Standards, Classification of Standards

Standard- The term standard is applied to a piece of equipment having a known measure of physical quantity. They are used for purposes of obtaining the values of physical properties of other equipment by comparison methods Classification of Standards

1. International standard: It is a standard recognised by an international agreement to serve internationally as the basis for assigning values to other standards of the quantity concerned. 2. National standard: It is a standard recognised by an international agreement to serve nationally as the basis for assigning values to other standards of the quantity concerned. 3. Primary standard: It is standard whose value is accepted without reference to other standards of the same quantity. 4. Secondary standard: It is standard whose value is assigned by comparing with a primary standard of same quantity. 5. Working standard: It is a standard that is used to calibrate or check the measuring instruments. 6. Reference standard: It is a standard having the highest metrological quality available at a given location from which measurements are made. 7. Transfer standard: It is a standard used as an intermediate to compare standards. 8. Travelling standard: It is used for construction, transport between locations.