## CLASS XI MH – PCMB Physics -Measurement Demo Videos

What are these quantities in physics called us weight you hear about it weight a person weight 20 kg length height a person’s height is 5.6 feet temperature it’s too cold the temperature today is 20 degrees Celsius  it’s too hot the temperature is 45 degrees celsius temperature pressure the pressure inside a can is 20 kg per meter square basically pressure and time so what are these quantities or what so common in these quantities yes all these quantities are called as physical quantity weight height time length temperature pressure all these are called as physical quantity now what is a physical quantity how do you signify that they’re called a physical quantity how will come to know ahead in your topics when some physical quantity comes how to identify them that they are a physical quantity obviously you can see there’s a common thing in all these quantities which are written on the screen there’s a common thing that is these things can be measured yes can you measure the height of course yes can you measure the length of any kind of object yes can you measure the weight, weight of a body weight of a person yes can you measure time temperature pressure of obviously yes  . anything which can measure is called as a physical quantity so basically let’s come to the definition of a physical quantity the first thing in your chapter a physical quantity is a quantity that can be measured is called as a physical quantity so any kind of a quantity which can be measured is called as a physical quantity examples you can go on length mass velocity temperature area volume density anything which comes to your mind which can be measured is called as a physical quantity let’s classify the physical quantity now the physical quantities are classified into two parts are two types the first kind of physical quantity is called as fundamental quantity and the second kind is called as derived quantity so fundamental quantity and derived quantity they are the classification for physical quantity or physical quantity is classified into fundamental quantity and derived Quantity let’s understand them one by one let’s understand first what is a fundamental quantity now if i consider fundamental quantity as the word suggests ok let’s read this definition of physical quantity which does not depend on any other physical quantity for its measurement is called as a fundamental physical quantity what does it mean it means it is that kind of a physical quantity which does not depend which does not you can say of correlate or you can say being produced by any other physical Quantity it’s a completely independent quantity so that’s why it’s called as a fundamental quantity now let’s understand by taking some examples obviously would be curious Ok. ok sir understood that the physical quantity which does not depend on any other physical quantity or which is completely independent is called as a fundamental physical quantity but give us some examples so here are some examples basically here’s the list of the enter fundamental quantities which we consider in this case fundamental quantities list we have got total seven ,seven fundamental quantities listed at below up in this case please understand them by heart them there are only seven fundamental quantities out of which we can derive some other but then independent quantities are only seven the first fundamental quantity is called as in this case length, length is the basic fundamental quantity whose SI units are taken as a meter and simple is taking the second fundamental quantity is mass SI units taken as in kilogram symbol kg the third fundamental quantity is time SI unit second symbol is a S understand this all these quantities which I’m listing our fundamental what do you mean by fundamental they do not depend on any other physical quantity for their existence or for their explanation if i consider mass if i consider  time they do not depend on any other quantity like if i say the time is 2 hours then it does not depend on the length of a room it does not depend on the temperature of the country or you can see the space where you are standing time is time, time in this case is not dependent on any other physical quantity hence it’s called as a fundamental quantity let’s move on in the list the fourth fundamental quantities temperature SI units of temperature is Kelvin and symbol k. fifth quantity electric current yes electric current is a fundamental quantity it’s not a any other derived kind of a quantity ok so electric current SI units ampere represented as a symbol as A then luminous intensity its SI units are candela represented as cd in this case what does luminous intensity understand in this case what the explanation for That what does it mean will understand later first will just list down so luminous Intensity it’s SI units candela then there is a 7 thing amount of substance which is measured at SI units mole represented as a mol so there are seven fundamental qualities and these are the list of the seven fundamental quantities I just revise the seven fundamental quantities are length mass time temperature electric current luminous intensity and amount of substance here Now along with this there were two more extra supplementary quantities which derive later which would explain later they were not put in the list of the fundamental quantities but they were categorized in a different list called as a supplementary list or a supplementary quantity list and these two supplementary quantities are the first one is called as a plane angle SI units taken as radians and symbol taken as rad the second supplementary quantities solid angle represented as an SI unit steradion  and symbol sr so it just remember there are seven fundamental quantities and there are two supplementary quantities