All Solutions

Sunday, January 2, 2022

What are physical quantities?

Solution: - All quantities in terms of which laws of physics can be explained and which can be measured directly or indirectly are called physical quantities. For example- mass, length, time, etc. Along with these physical quantities, you should also go through Scientific Instruments and their uses and to improve your knowledge, please refer to All Inventors and their inventions.


What are physical quantities?
What are physical quantities?




Table of Knowledge- 

1. What are physical quantities

What are physical quantities

Solution: - Basically physical quantities are classified into the following two categories-

i.      Fundamental Physical quantities

ii.   Derived Physical quantities


i.    Fundamental Physical quantities:- Those physical quantities that do not depend on other physical quantities are known as fundamental physical quantities. Such as – mass, length, time, etc.


ii.  Derived Physical quantities: -Those physical quantities that are obtained from the fundamental physical quantities are known as derived physical quantities. Such as force, momentum, etc.

 

Before we dip into the topic, we must know about the ‘Unit’ of physical quantities

 

Definition of unit: - The value assigned to the measurement of physical quantities is called unit.


The following points should be kept in mind when we select the unit of any physical quantity.

     a.    The selected unit should be valid, reasonable size and quantity.

     b.    The selected unit can be easily defined and in each place, their counterparts can be easily created. 

     c.    The selected unit is not affected by heat, pressure, and time change.


Systems of units

There are three methods of units systems

i.     Centimeter -gram-second (CGS)system

ii.  Meter-kilogram-second (MKS) system

iii. Foot-pound-second (FPS)system


i.    C.G.S. system: - It is a French system of units. In this system, length is measured in centimeters, mass is grams and time is measured in seconds.


ii.  M.K.S system: - It is also a French system. In this system, length is measured in meter, mass in kilogram, and time in seconds.


iii.  F.P.S system: - It is a British system of units. In this system, length is measured in the foot, mass in pounds, and time in seconds.

 

 

7(Seven) fundamental physical quantities and their units

 

 

S.No.

Physical quantity

Unit & symbol

1

Length

Meter (m)

2

Mass

Kilogram (Kg)

3

Time

Seconds(s)

4

Temperature

Kelvin(K)

5

Electric current

Ampere (A)

6

Luminous intensity

Candela (Cd)

7

Amount of substance

Mole(mol)


  • There are two other units defined besides these 7(Seven) fundamental physical quantities and their units. These are known as ‘supplementary units.

 

 

S.No.

Physical quantity

Unit & symbol

1

Plane angle

Radian(rad)

2

Solid angle

Steradian(sr)

 

 

 

 

Now we will discuss about derived physical quantities

     ·      Unit of force = Newton = Kg m/s2

     ·      Unit of power= Watt = J/s

      ·      Unit of pressure =Pascal= N/m2

·       

Major physical quantities and their units


 Here you are provided major physical quantities their units


 

 

 

 

 

Physical Quantity            

 

S.I. Unit             

Symbol

 

Length                                                                                                                                                                          

meter

m

 

Mass                                                                                                                                                                          

kilogram

kg

 

Time                                                                                                                                                                                                                               

second

s

 

Energy / Work                                                                                                                                                                                                                                    

Joule

J

 

Electric current                                                                                   

Ampere

A

 

Temperature                                                                     

Kelvin

K

 

1Force                                                                                    

Newton

N

 

Light intensity                                                                                  

Candela

Cd

 

Speed                                                                                              

Meter/second

m/s

 

Frequency                                                                                               

Hertz

Hz

 

Pressure                                                                                                   

Pascal

Pa

 

Momentum                                                                     

Kilogram-meter/sec

Kg -m/s

 

Inertia                                                                                   

Kilogram-meter2

Kg-m2

 

Speed                                                                                               

Meter/sec

m/s

 

Power                                                                                                     

watt

W

 

Surface tension                                                       

Newton/meter

N /m

 

Angular velocity                                                                  

Kilogram. Meter/sec

Kg-m/s

 

Electric charge                                                                                   

Coulomb

C

 

Potential difference                                                                               

Volt

V

 

Potential                                                                                                 

Volt

V

 

Resistance                                                                                                 

Ohm

 

Power capacity                                                                                   

Faraday

F

 

Specific resistance/ Resistivity                                                   

Ohm -meter

Ωm

 

Distance                                                                                              

Meter

M

 

Displacement                                                                                      

Meter

m

 

Velocity                                                                                  

Meter/sec

m/s

 

Magnetic flux                                                                                   

weber

Wb

 

Power of lens                                                                                        

diopter

D

 

Focal length                                                                                

centimeter

cm

 

Acceleration                                                                                                     

Meter/sec2

m/s2

 

Area                                                

meter square                                           

m2

 

Volume                                           

 

meter cube                                             

M3

 

Gravitational acceleration               

meter/sec2                                               

m/s2

 

 

Density

 

kilogram/meter cube

Kg/m3

 

So, these are physical quantities and their units. Now we will discuss ‘International definition of Fundamental Units’


International definition of Fundamental Units


      1.    Meter: - One meter is the distance traveled/covered by light in a vacuum in 1/299792458 of a second.


      2.    Kilogram: - General conference of weights and measures described kilogram as the mass of platinum Irridium cylinder kept at the Bureau of weight and measures at Sevres, Paris, France.


     3.    Second: - One second is equal to the duration of 9,192,631,770 vibrations corresponding to the transition between two hyperfine levels of Caesium 133 atom in the ground state.


     4.     Ampere: - One ampere is the constant current which means maintain in each of the two straight parallel current-carrying conductors of the infinite length of the negligible area of cross-section and held one meter apart in vacuum produce a force of 2×10-7 Nm-1 between them.


     5.    Kelvin: - Kelvin is the fraction 1/273.16 of the thermodynamical temperature of the triple point of water.


     6.    Candela: - One candela is that luminous intensity in a perpendicular direction of 1/600000 m2 area of a black body at the freezing point of Platinum under the pressure of 101.325Nm-2.


     7.    Mole: - One mole is that amount of substance that contains as many elementary entities as there are atoms in 0.012Kg of pure 6C12


Check yourself

    1.  What is the unit of luminous intensity in the S.I. system?

    2.  What is the unit of Planck’s constant?

    3.  Joule is the unit of which physical quantity?

    4.  What is the unit of frequency?

    5.  Ohm meter is the unit of which physical quantity?  


     Related Searches 

General Knowledge

Scientific Instruments list and  their Uses



Frequently asked questions


 1. What are physical quantities and their types?

Physical quantities are the quantities that can be measured directly or indirectly. They are of two types- (i). Fundamental physical quantities (ii). Derived physical quantities.

 

2. What are some examples of physical quantities?

There are many physical quantities in physics we study about, here are some examples – length, mass, time. electric current etc.

 

3. What are supplementary physical quantities?

In physics, there are two supplementary physical quantities- plane angle and solid angle.

 

4. What is a fundamental physical quantity?

The physical quantities that do not depend on other physical quantities are known as fundamental physical quantities. Such as – mass, length, time, etc.

 

5. Which physical quantities can never be negative?

There are many physical quantities that can be negative like acceleration, force, momentum can be negative and they can be positive.

 

                                   Top 

 




No comments:

Post a Comment