Presentation1.pdf
- 1. MEASUREMENT
- 2. Measurement in everyday life Measurement of mass Measurement of volume
- 3. Measurement in everyday life Measurement of length Measurement of temperature
- 4. Need for measurement in physics • To understand any phenomenon in physics we have to perform experiments. • Experiments require measurements, and we measure several physical properties like length, mass, time, temperature, pressure etc. • Experimental verification of laws & theories also needs measurement of physical properties.
- 5. Physical Quantity A physical property that can be measured and described by a number is called physical quantity. Examples: • Mass of a person is 65 kg. • Length of a table is 3 m. • Area of a hall is 100 m2. • Temperature of a room is 300 K
- 6. Types of physical quantities 1. Fundamental quantities: The physical quantities which do not depend on any other physical quantities for their measurements are known as fundamental quantities. Examples: • Mass • Length • Time • Temperature
- 7. Types of physical quantities 2. Derived quantities: The physical quantities which depend on one or more fundamental quantities for their measurements are known as derived quantities. Examples: • Area • Volume • Speed • Force
- 8. Units for measurement The standard used for the measurement of a physical quantity is called a unit. Examples: • metre, foot, inch for length • kilogram, pound for mass • second, minute, hour for time • fahrenheit, kelvin for temperature
- 9. Characteristics of units Well – defined Suitable size Reproducible Invariable Indestructible Internationally acceptable
- 10. • This system was first introduced in France. • It is also known as Gaussian system of units. • It is based on centimeter, gram and second as the fundamental units of length, mass and time. CGS system of units
- 11. MKS system of units • This system was also introduced in France. • It is also known as French system of units. • It is based on meter, kilogram and second as the fundamental units of length, mass and time.
- 12. FPS system of units • This system was introduced in Britain. • It is also known as British system of units. • It is based on foot, pound and second as the fundamental units of length, mass and time.
- 13. International System of units (SI) • In 1971, General Conference on Weight and Measures held its meeting and decided a system of units for international usage. • This system is called international system of units and abbreviated as SI from its French name. • The SI unit consists of seven fundamental units and two supplementary units.
- 14. Seven fundamental units FUNDAMENTAL QUANTITY SI UNIT SYMBOL Length metre m Mass kilogram kg Time second s Temperature kelvin K Electric current ampere A Luminous intensity candela cd Amount of substance mole mol
- 15. Definition of metre The metre is the length of the path travelled by light in a vacuum during a time interval of 1/29,97,92,458 of a second.
- 16. Definition of kilogram The kilogram is the mass of prototype cylinder of platinum-iridium alloy preserved at the International Bureau of Weights and Measures, at Sevres, near Paris.
- 17. Prototype cylinder of platinum-iridium alloy
- 18. Definition of second One second is the time taken by 9,19,26,31,770 oscillations of the light emitted by a cesium–133 atom.
- 19. Two supplementary units 1. Radian: It is used to measure plane angle θ = 1 radian
- 20. Two supplementary units 2. Steradian: It is used to measure solid angle Ω = 1 steradian
- 21. Rules for writing SI units 1 Full name of unit always starts with small letter even if named after a person. • newton • ampere • coulomb not • Newton • Ampere • Coulomb
- 22. Rules for writing SI units 2 Symbol for unit named after a scientist should be in capital letter. • N for newton • K for kelvin • A for ampere • C for coulomb
- 23. Rules for writing SI units 3 Symbols for all other units are written in small letters. • m for meter • s for second • kg for kilogram • cd for candela
- 24. Rules for writing SI units 4 One space is left between the last digit of numeral and the symbol of a unit. • 10 kg • 5 N • 15 m not • 10kg • 5N • 15m
- 25. Rules for writing SI units 5 The units do not have plural forms. • 6 metre • 14 kg • 20 second • 18 kelvin not • 6 metres • 14 kgs • 20 seconds • 18 kelvins
- 26. Rules for writing SI units 6 Full stop should not be used after the units. • 7 metre • 12 N • 25 kg not • 7 metre. • 12 N. • 25 kg.
- 27. Rules for writing SI units 7 No space is used between the symbols for units. • 4 Js • 19 Nm • 25 VA not • 4 J s • 19 N m. • 25 V A.