Units
[Disclaimer: I just wanted to share some things which I am learning.Kindly confirm those from the textbooks.]

Hello friends,

In this website we will learn about units. This chapter of Units is very important while learning physics. For IIT JEE exam this chapter is important. So let us learn about units.

1.1 – Physical Quantity

Physical quantity is a quantity which can be measured & by which various physical happenings can be explained in the form of laws. Length, Mass, Time, Force, Energy, etc. are the examples of a physical quantity.

1.2 – Measurement

Measurement is important to compare two similar quantities. It is also necessary to determine the magnitude of a physical quantity & to prove some physical laws. We can find the magnitude of a physical quantity. When we colour our room, we measure the length, breadth & height of that room. After measuring the length, breadth & height of the room, we can give the colour to the room.

A physical quantity is completely represented by its magnitude & its unit. For example, 20 m means a length which is 20 times that of unit of length. Here, meter is a unit of length. So we can say that 20 m means a length which is 20 times that of unit of length. Here is the formula of a physical quantity.

Physical Quantity (Q) = Magnitude X Unit = n X u

1.3 – Fundamental Quantity

We know that there are a large number of quantities are there in our vast world. But out of these only few are independent. In SI system of units there are only seven quantities are independent. The quantities which are independent of all other quantities & do not require the help of any other physical quantity for their definition. Such quantities are said to be fundamental quantities. The fundamental quantities in SI System are given below in this chart.

There are supplementary quantities also in SI system. Here is a chart of the supplementary quantities & their SI Unit.

1.4 – Derived Quantities

The quantities which are not fundamental quantities are derived quantities. This is just a simple definition. But what is the main definition of derived quantities? The quantities which are not independent & do require the help of any other fundamental quantity for their definition. Such quantities are said to be derived quantities. For example, Force, Volume, Energy, etc. are derived quantities.

1.5 – Fundamental & Derived Units

The units of fundamental quantities are said to be fundamental units & the units of derived quantities are said to be derived units. So meter, second, time, kelvin, etc. are fundamental units & newton, area, volume, etc. are derived units.

1.6 – System of units

There are three common systems which we use in our everyday life. These three systems and their units are given below in this chart.

 

1.7 – Thank you

So friends thank you for watching my website. Best of luck for your exams… See you next time.

Your friend,

Aditya P