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है”ह”ह

IS 1885-73-1 (1993): Electrotechnical Vocabulary, Part 73:Physics and chemistry, Section 01: Physical concepts [ETD1: Basic Electrotechnical Standards]

July 1993

Indian Standard

ELECTROTECHNICALVOCABULARY PART 73 PHYSICS AND CHEMISTRY

Section 1 Physical Concepts

UDC 530-19 : 621-3.01 : 001.4

Q BIS 1993

BUREAU OF INDIAN STANDARDS MANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Price! Group 4

Basic Electrotechnical Standards Sectional Committee, ET 01

NATlONAL FOREWORD

This Indian Standard ( Part 73/Set 1 ) which is identical with IEC Pub 50 ( 111-01 ) ( 1982 ) ‘Inter- national eiectrotechnical vocabulary - Chapter 111 : Physics and Chemistry, Section 01 : Physical concepts’ issued by International Electrotechnical Commission ( IEC ), was adopted by the Bureau of Indian Standards on the recommendation of the Basic Electrotechnical Standards Sectional Committee, ET 01 and approval of the Electrotechnical Division Council.

Only the English text given in the IEC Publication has been retained while adopting as Indian Standard, and as such the page numbers given here are not same as in IEC Publication.

IS 1885 ( 1’at-t 73/Set 1 ) : lY93

II3 iJut) 50 ( 11141 ) ( 1982 )

Indian Standard

ELECTROTECHNICALVOCABULARY PART 73 PHYSICS AND CHEMISTRY

Section 1 Physical Concepts

EXPLANATORY NOTE

Thepurposeof I.E.V.advanceeditionsisto permit theissuewithout!ossof timeof terminologyworkwhose publication would otherwise be delayed and, in particular, workwhich does not exaclly correspond to the general plan of the IEV.: for example, incomplete chapters, vocabularies extending beyond the framework of a normal chapter or work relatmg to rapidly evolving fields. Advance editions may, in certain cases. he incomplete, particular!y as regards the Russian text and the terms in the additional languages, when the appropriate information is not available at the time of printing.

Remarks:

1. In the following definitions, “body” is used in its most general sense including the solid, liquid and gaseous forms of a given sample of matter.

2. The phrase “quantity Aper unit of quantity B” means the limit of the quotient of quantity AA by quantity A B, i.e. Iim (A A/A B)

AB+O

3. In every branch of physics it is necessary to accept a minimum number of axioma tic con- cepts. In section 111 A --+ 01, mass and electric charge are introduced axiomatically.

111-01-01

iiiertia

That property of matter by virtue ofwhich any material body continues in its existing state of movement or rest, in the absence of an external force.

111-01-02

mass (m)

,$ fundamental quantity axiomatically designed to describe inertia and gravitation.

111-01-03

(linear) momentum (p) 1. For a particle, a vector quantity equal to the

product of its mass and its velocity.

2. For a body, the vector sum of the momenta of its constituent particles.

111-01-04

(mechanical) force (F)

A vector quantity equal to the time derivative of the linear momentum.

Note. - When the mass is constant, the force is equal to the product of the mass of a body and its vector accelerd- lion.

111-01-05 moment of inertia (1)

(about an axis)

For a body, the pum of the products of the mass of each particle and the square of its distance from a given axis.

I = 2 (m; YY,

ill-0146

angular momentum

moment of momeutum

1. For a particle in motion, a quantity equal to the vcctorproduct ofthe radius vector and the linear momentum.

2. For a body in motion, the vector sum of the angular momenta of its constituent particles.

Note - The angular momentum of a rigid body rotating around a fixed axis is equal to the product of the moment of inertia and the angular velocity vector.

111-01-07

moment of a force (at a point) (M)

At a point A, the quantity given by the vector product

of the vector G by the tbrcc 7 applied at the point B.

111-01-08 -

torque (about a point) (T)

The sum of the moments of a set of forces about a point.

Note. - If the resultant of the forces is zero, the torque is independent of the point chosen.

111-01-09

work(W)

Aquantity equal to the scalar product of a force and the corresponding displacement vector.

111-01-10 energy (E )

A quantity characterizing the ability of a physical sys-

tern to do work. Note. - Energy exists in different forms transformable one

into the other examples are mechanical, electromagnetic, chemical, thermal, neclear, etc.

1

1s 18X5 ( k-t :3/srr 1 ) : 1993

IEC PutI 50 ( Ill-01 ) ( 1982 )

111-01-11 power (P )

The time rate of transferring or transforming energy, or of doing work.

111-01-12

stress

The force per unit area acting upon a bddy which tends to change the dimensions of the latter.

111-01-13

strain

Deformation produced in a body as the result of stress.

111-01-14

pressure (in a fluid) (u)

A type of stress, characterized by its unifonnity in all directions.

111-01-15

thermal energy (Q)

heat energy

The internal kinetic energy of a body, related to the disordered tnotions of its constituents.

111-01-16

(thermodynamic) temperature (T)

Astate variable proportional to the thermal energy of a given body at equilibrium.

111-01-17

internal energy (Or)

The function of state equal to the sum of the work and the thermal energy that would be delivered by a body during cooling to the thermodynamic tempera’ ‘re of zero kelvin.

111-01-18

enthalpy (H)

A tinction of state equal to the sum of the internal energy of a body and the product of its pressure and its volume.

ill-01-19 entropy (S)

H=U+yV

A function of state whose differential during a revers- ible transformation is

dS = 6 Q/T

where 6 Q is the thermal energy supplied to the physi- cal system by the external environment at ther- modynamic temperature 7:

N&e. - Entropy is related to the degree of disorder of a physical system.

111-01-20 quantum

The smallest amount of a physical quantity that can be associated with a given phenomenon, when the observ- able quantity is restriced to a discrete set of values.

2

111-01-21 photon

A quantum of electromagnetic energy Izv with some particle-like characteristics, where k is the Planck con- stant and v the frequency of radiation.

111-01-22

phonon

A’ quantum of mechanical vibratory energy with par- ticle-like characteristics.

111-01-23

electric charge (Qj

A fundamental quantity axiomatically defined to describe certain experimentally observed interactions.

111-01-24 elementary (electric) charge (e)

The magnitude of the quantum of electric charge (0.160219 x lo-‘* $I).

111-01-25

atom

The smallest particle into which a chemical element can be divided while retaining its chemical properties.

111-01-26

nucleus

The central part of an atom having a positive charge and nearly ail the mass of the atom.

111-01-27 electron

A stable elementary particle with one negative elemen- ta y charge and a rest mass of 0.91095 x 10P3’ kg.

lvc?tc - ‘The term electron is sometimes used loosely to include both electrons and positrons.

111-01-28

positron

An elementary particle with practically the same mass as the electron but with a positive elementary charge.

ill-Ol-2Y

proton

A stable elementary particle with one positive elemen- tary charge and a rest mass of 1.67265 x 10ez7 kg.

111-01-30 mean life (of a particle)

In an exponentially decaying population, the time in which the number of particles is divided by e, the base of naperian logarithms.

111-01-31

neutron

An elementary particle having no electric charge, a rest mass approximately equal to that of a proton and in the free state a mean life of about 1000 s.

._. . ..----.--- _, ),_,_ “__X-,-II_-.---..~l--- _._, I..

-- _.^_. -- .- I ..- _”

“,_, .n,.. “l.,le. 1.1, . ‘.., l i . l ..I

111-01-32 nucleon

Generic term for a constituent 0C an atomic nucleus, either proton or neutron.

111-01-33 mass number (of a nucleus) (A)

The total number of nucleons contained in a nucleus.

111-01-34

atomic number (2)

The order of an element in the periodic (Mendeleev) chemical classification, identified with the number of protons in the nucleus.

Note. -- Z =A - N where N is the number of neutrons in the nucleus.

111-01-35 nuclide

A species of atom characterized by its mass number, atomic number and nuclear energy state, provied that the mean life in that state is long enough to be observable.

111-01-36

isotope

One of a set of nuclides having the same lumber of protons, hence constituting the same chemical element, but differing in number of neutrons.

111-01-37

free electron

An electron, not directly associated with the structure of an atom or molecule, free to move under the infIuence of an applied electric field.

111-01-38

energy level

The energy associated with a quantum state of a physical system.

111-01-39

bound electron

An electron in one of the quantized energy levels of an atom or molecule, not free to move under the influence of an applied electric field.

111-01-40

valence electron

An electron, usually in the outer shell of the structure of an atom, commonly the means by which the atom enters into chemical combinations.

111-01-41 molecule

A particle comprising a group of atoms bonded by valence electrons and forming a structure that persists as a unit through changes of physical state.

111-01-42 ion

Any atom or bonded group of atoms that has a net electric charge.

IS 18X5 ( Part 73/&c I ) : 1993

115C 1’111) 50 ( 111-01 ) ( 1982 )

111-01-43 ionization

The formation of ions.

111-01-44 electron gas

An aggregate of free electrons exhibiting some proper- ties of a gas.

111-01-45

ground state

The state corresponding to the lowest energy level.

111-01-46 excited state

A state corresponding to an energy level higher than that of the ground state.

111-01-47 excitation energy

The energy necessary to raise a quantized system from the ground state to a given excited state.

111-01-48

resonance state

An excited state from which the transition directly to the ground state by emission of a photon is permitted.

111-01-49

metastable state

Ao excited state from which the transition to a state of lower energy is normally forbidden.

Note. - The energy is often transferred to another particle ‘3uch as molecule, atom or electron.

111-01-50 energy band

A virtually continuous WI of energy levels in a sub- stance.

111-01-51 permitted band

An energy band each level of which may be occupied by electrons.

111-01-52 forbidden band

An energy band that cannot be .occupied by electrons.

ill-01-53 energy gap

The smallest energy difference between two neigh- bouring permitted bands separted by a forbidden band.

111-01-54

Fermi (characteristic energy) level

In a solid, the energy level separating the occupied states from the unoccupied states at a thermodynamic temperature of zero kelvin. Note. - When a forbidden band separates the occupied and

unoccupied states, the Fermi level is generally as- signed to the centre of the forbidden band.

3

IS 1885 ( Part 73/Set 1 ) : 1993

1Fx: PIllI 50 ( Ill-01 ) ( 1982 )

111-01-55 valence band

The permitted band occupied by the valence electrons.

111-01-56 conduction band

A permitted band incompletely occupied by electrons.

111-01-57

conduction electron

An electron of a conduction band free to move under the influence of an electric field.

111-01-58

hole

Avacancy appearing in a normally-filled cncrgy band, behaving like a positive charge carrier.

Note. - A hole is frequently produced by the elevation of an electron from thevalence band to the conduction band and produces what is called an electmn-holepuir

111-01-59

charge carrier

P. particlc such as an electron, proton, ion and, by extension, a hole, having one or more elementary electric charges.

111-01-60

electron emission

The release of electrons from the surface of a body into the adjacent space.

111-01-61

thermionic emission

Electron emission due to thermal agitation.

111-01-62

photoelectric etnission

Electron emission due to the incidence of photons.

111-01-63

field emission

Electron emission due to the action of a strong electric field.

111-01-64

primary-electron emission

Thermionic, photoelectric or field emission.

111-01-6s

secotldary-electron emission

Electron emission due to the bombardment ofthc emit- ting surlYIce by rlectron~ or ions.

111-01-66 work function

The least energy required for the emission of a cc&ut lion electron.

M-01-67 mobility (of a charge carrier)

A quantity equal to the quotient of the modulus of the

mean velocity of a charge carrier in the direction of r_ an electric field by the modulus of the strength of this - field.

111-01-68 mean free path

The average distance travelled by a particle between two successive collisions with other particles.

111-01-69

collision of the first kind

A collision in which a quantum of energy given to an atom is supplied by the incident particle.

111-01-70

collision of the second kind

A collision in which the quantum or quanta of energy taken from an atom increase the energy of the incident particle.

111-01-71

effective collision cross-section

The probability of collision per unit path-length of the incident particles divided by the number density of the particles constituting the target.

111-01-72

ionization energy

The least energy necessary to ionize an atom or molecule from its ground state.

111-M-73

probability of ionization

(by collision)

The ratio of the number of collisions followed by ionization to the total number of collisions during a specified time.

111-01-74

s$ecitied ionization coefficient

The average number of pairs of ions of opposite sign that a particle with a given kinetic energy produces per unit path length under specified conditions.

Note. - A positive ion and an electron are considered also to be a pair of ions.

111-01-75

ionization rate

The number of pairs of ions produced per unit volume per unit time.

11 I-O! -76

reccrnubination

LJnio:~ of charge carriers of opposite signs.

111-01-77 de-ionization

Recombination of ions in an ionized fluid.

4

111-01-78

recombination rate

The number of pairs of charge carriers recombined per unit volume per unit time.

111-01-79

de-ionization rate

The number of pairs of ions rccon&ined per unit volume per unit time.

IS 1x85 ( I’urt 73iSrr 1 ) : ;993

11X I’uh 50 ( 111-01 ) ( 1982 )

111-01-80

recombination coefficient

The quotient of recombination rate by the square of the charge carrier density of the recombining charges.

111-01-81

plasma

A conductive gaseous medium composed of free electrons, ions and neutral particles which macroscopi- tally IS approximately electrically neutral.

IS 1X85 ( Putt 73/St$ I ) : I9Y3

11-x‘ 1’111) 50 ( 11141 ) ( IYXZ )

A

angular momentum

atom

atomic number

B

bound electron

C

charge carrier 111-01-59 collision of the first kind 111-01-69 collision of the second kind 111-01-70 conduction band 111-01-56 conduction electron 111-01-57

D

de-ionization * 111-01-77 de-ionization rate 111-01-79

E

effective collision cross section 111-01-71 electric charge 111-01-23 electron 111-01-27 electron emission 111-01-60 electron gas 111-01-44

elementary (electric) charge 111-01-24 energy . 111-01-10 energy band 111-01-50

energy gap 111-01-53

energy level 111-01-38 enthalpy 111-01-18

entropy 111-01-19 excited stale 111-01-46 excitation energy 111-01-47

F

Fermi (characteristic energy) level

tield emission

forbidden band

free electron

force (mechanical)

G

ground state

heat energy ,$

hole

H

INDEX

111-01-06

111-01-25

111-01-34

111-01-39

111-01-54

111-01-63

111-01-52

111-01-37

111-01-04

111:01-45

111-01-15

111-01-58

inertia

internal energy ion

ionization

ionization energy

ionization rate

isotope

I

M

mass

mass number (of a nucleus) mean free path

mean life (of a particle)

mechanical force

metastable state

molecule

moment of a force (at a point)

moment of inertia (about an axis)

moment of momentum

mementum (linear)

mobility (of a charge carrier)

neutron

nucleon

nucleus

nuclide

N

P permitted band 111-01-51 phonon 111-01-22 photoelectricemission 111-01-62 photon 111-01-21 plasma I I l-01-81 positron 11 l-01-28 power 111-01-11 pressure (in a fluid) 111-01-14 primary-electron emission 111-01-64 probability of ionization (by collision) 111-01-73 proton 111-01-29

quantum

Q

R

recombination

recombination coefficient

recombination rate

resonance state

111-01-01

111-01-17

111-01-42

111-01-43

lli-01-72

111-01-75

111-01-36

111-01-02

111-01-33 111-01-68

111-01-30

111-01-04

111-01-49 111-01-41

111-01-07

111-01-05

111-01-06

111-01-03 111-01-67

111-01-31

111-01-32

11 l-01-26

111-01-35

111-01-20

111-01-76

111-01-80

111-01-78

111-01-48

6

s secondary-electron emission

specific ionization coefficient

strain

stress

T

temperature (thermodynamic)

thermal energy

thermionic emission,

111-01-65 torque (about a point)

111-01-74

111-01-13

lil-01-12 valence hand

valence electron

111-01-16 work

111-01-15 work function

1s 1885 ( I’M-t 73/&x! 1 ) : 199.1

IEC l’ub 50 ( Ill-01 ) ( 1982 )

111-01-61

111-01-08

V

111-01-55

l&1-01-40

W

111-01-09

111-01-66

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