Title Chapter 1 Units and Measurements.pdf ✅

PHYSICS Chapter 1: Units and Measurements
(1) 01 UNITS AND MEASUREMENTS Units and Measurements Units A unit is an internationally accepted standard for measurements of quantities. Measurement consists of a numeric quantity along with a relevant unit. Units for Fundamental or base quantities (like length, time etc.) are called Fundamental units. Units which are combination of fundamental units are called Derived units. Fundamental and Derived units together form a System of Units. Internationally accepted system of units is SystèmeInternationale d’ Unites (French for International system of Units) or SI. It was developed and recommended by General Conference on Weights and Measures in 1971. SI lists 7 base units as in the table below. Along with it, there are two units - radian or rad (unit for plane angle) and steradian or sr (unit for solid angle). They both are dimensionless. Base Quantity Name Symbol Length metre m Mass kilogram kg Time second s Electric Current ampere A Thermo dynamic Temperature kelvin K Amount of Substance mole mol
(2) 01 UNITS AND MEASUREMENTS Luminous intensity candela cd Base Quantity Name Symbol Length metre m Mass kilogram kg Time second s Electric Current ampere A Thermo dynamic Temperature kelvin K Amount of Substance mole mol Luminous intensity candela cd Base Quantity Name Symbol Length metre m Mass kilogram kg Time second s Electric Current ampere A Thermo dynamic Temperature kelvin K Amount of Substance mole mol
(3) 01 UNITS AND MEASUREMENTS Luminous intensity candela cd Measurement of Length Length can be measured using metre scale (10-3m to 102m), verniercallipers (10-4m) and screw gauge and spherometer (10-5m). Range of Length Size of object or distance Length (m) Size of proton 10-15 Size of atomic nucleus 10-14 Length of typical virus 10-8 Wavelength of light 10-7 Thickness of paper 10-4 Height of Mount Everest above sea level 104 Radius of earth 107 Distance of moon from earth 108 Distance of sun from earth 1011 Distance of pluto from sun 1013