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?

Table of Knowledge- 

1. What are physical quantities

 i.Fundamental Physical Quantities

ii. Derived Physical Quantities

iii. Definition of Unit

2. System of Units

3.SevenFundamental Physical Quantities

4.Major physical quantities and their units

5. International definition of Fundamental Units

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	Ω
	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