Физические законы, переменные, принципы

the thermodynamic temperature at constant pressure.

The pressure law. The pressure of an ideal gas is directly

proportional to the thermodynamic temperature at constant volume.

Joule-Thomson effect; Joule-Kelvin effect (J. Joule, W. Thomson)

The change in temperature that occurs when a gas expands into aregion

of lower pressure.

Joule's laws

Joule's first law. The heat produced when an electric current flows

through a resistance for a specified time is equal to the square of the

current multiplied by the resistivity multiplied by the time.

Joule's second law. The internal energy of an ideal gas is independent

of its volume and pressure, depending only on its temperature.

Josephson effects (B.D. Josephson; 1962)

Electrical effects observed when two superconducting materials

areseparated by a thin layer of insulating material.

Kepler's laws (J. Kepler)

Kepler's first law. A planet orbits the Sun in an ellipse with the Sun

at one focus.

Kepler's second law. A ray directed from the Sun to a planet sweeps out

equal areas in equal times.

Kepler's third law. The square of the period of a planet's orbit is

proportional to the cube of that planet's semimajor axis; the constant of

proportionality is the same for all planets.

Kerr effect (J. Kerr; 1875)

The ability of certain substances to differently refract lightwaves

whose vibrations are in different directions when thesubstance is placed in

an electric field.

Kirchhoff's law of radiation (G.R. Kirchhoff)

The emissivity of a body is equal to its absorptance at the

sametemperature.

Kirchhoff's rules (G.R. Kirchhoff)

The loop rule. The sum of the potential differences encountered in a

round trip around any closed loop in a circuit is zero.

The point rule. The sum of the currents toward a branch point is equal

to the sum of the currents away from the same branch point.

Kohlrausch's law (F. Kohlrausch)

If a salt is dissolved in water, the conductivity of the solutionis the

sum of two values -- one depending on the positive ions andthe other on the

negative ions.

Lambert's laws (J.H. Lambert)

Lambert's first law. The illuminance on a surface illuminated by light

falling on it perpendicularly from a point source is proportional to the

inverse square of the distance between the surface and the source.

Lambert's second law. If the rays meet the surface at an angle, then

the illuminance is also proportional to the cosine of the angle with the

normal.

Lambert's third law. The luminous intensity of light decreases

exponentially with the distance that it travels through an absorbing

medium.

Landauer's principle

A principle which states that it doesn't explicitly take energy

tocompute data, but rather it takes energy to erase any data,since erasure

is an important step in computation.

Laplace's equation (P. Laplace)

For steady-state heat conduction in one dimension, the

temperaturedistribution is the solution to Laplace's equation, which

statesthat the second derivative of temperature with respect todisplacement

is zero.

Laue pattern (M. von Laue)

The pattern produced on a photographic film when high-

frequencyelectromagnetic waves (such as x-rays) are fired at a

crystallinesolid.

Laws of conservation

A law which states that, in a closed system, the total quantity

ofsomething will not increase or decrease, but remain exactly thesame. For

physical quantities, it states that something canneither be created nor

destroyed.

The most commonly seen are the laws of conservation of mass-energy

(formerly two conservation laws before A. Einstein), ofelectric charge, of

linear momentum, and of angular momentum.There are several others that deal

more with particle physics,such as conservation of baryon number, of

strangeness, etc., whichare conserved in some fundamental interactions but

not others.

Law of reflection

For a wavefront intersecting a reflecting surface, the angle

ofincidence is equal to the angle of reflection.

Laws of black hole dynamics

First law of black hole dynamics. For interactions between black holes

and normal matter, the conservation laws of total energy, total momentum,

angular momentum, and electric charge, hold.

Second law of black hole dynamics. With black hole interactions, or

interactions between black holes and normal matter, the sum of the surface

areas of all black holes involved can never decrease.

Laws of thermodynamics

First law of thermodynamics. The change in internal energy of a system

is the sum of the heat transferred to or from the system and the work done

on or by the system.

Second law of thermodynamics. The entropy -- a measure of the

unavailability of a system's energy to do useful work -- of a closed system

tends to increase with time.

Third law of thermodynamics. For changes involving only perfect

crystalline solids at absolute zero, the change of the total entropy is

zero.

Zeroth law of thermodynamics. If two bodies are each in thermal

equilibrium with a third body, then all three bodies are in thermal

equilibrium with each other.

Lawson criterion (J.D. Lawson)

A condition for the release of energy from a thermonuclearreactor. It

is usually stated as the minimum value for theproduct of the density of the

fuel particles and the containmenttime for energy breakeven. For a half-

and-half mixture ofdeuterium and tritium at ignition temperature, nG t is

between1014 and 1015 s/cm3.

Le Chatelier's principle (H. Le Chatelier; 1888)

If a system is in equilibrium, then any change imposed on thesystem

tends to shift the equilibrium to reduce the effect of thatapplied change.

Lenz's law (H.F. Lenz; 1835)

An induced electric current always flows in such a direction thatit

opposes the change producing it.

Loschmidt constant; Loschmidt number; NL

The number of particles per unit volume of an ideal gas atstandard

temperature and pressure. It has the value 2.68719.1025 m-3.

Lumeniferous aether

A substance, which filled all the empty spaces between matter,which was

used to explain what medium light was "waving" in. Nowit has been

discredited, as Maxwell's equations imply thatelectromagnetic radiation can

propagate in a vacuum, since theyare disturbances in the electromagnetic

field rather thantraditional waves in some substance, such as water waves.

Lyman series

The series which describes the emission spectrum of hydrogen

whenelectrons are jumping to the ground state. All of the lines arein the

ultraviolet.

Mach's principle (E. Mach; 1870s)

The inertia of any particular particle or particles of matter

isattributable to the interaction between that piece of matter andthe rest

of the Universe. Thus, a body in isolation would have noinertia.

Magnus effect

A rotating cylinder in a moving fluid drags some of the fluidaround

with it, in its direction of rotation. This increases thespeed in that

region, and thus the pressure is lower.Consequently, there is a net force

on the cylinder in thatdirection, perpendicular to the flow of the fluid.

This is calledthe Magnus effect.

Malus's law (E.L. Malus)

The light intensity travelling through a polarizer is proportionalto

the initial intensity of the light and the square of the cosineof the angle

between the polarization of the light ray and thepolarization axis of the

polarizer.

Maxwell's demon (J.C. Maxwell)

A thought experiment illustrating the concepts of entropy. Wehave a

container of gas which is partitioned into two equal sides;each side is in

thermal equilibrium with the other. The walls(and the partition) of the

container are a perfect insulator. Now imagine there is a very small

demon who is waiting at thepartition next to a small trap door. He can

open and close thedoor with negligible work. Let's say he opens the door

to allow afast-moving molecule to travel from the left side to the right,

orfor a slow-moving molecule to travel from the right side to the left, and

keeps it closed for all other molecules. The net effectwould be a flow of

heat -- from the left side to the right -- eventhough the container was in

thermal equilibrium. This is clearlya violation of the second law of

thermodynamics. So where did we go wrong? It turns out that information

hasto do with entropy as well. In order to sort out the moleculesaccording

to speeds, the demon would be having to keep a memory ofthem -- and it

turns out that increase in entropy of the simplemaintenance of this simple

memory would more than make up for thedecrease in entropy due to the heat

flow.

Maxwell's equations (J.C. Maxwell; 1864)

Four elegant equations which describe classical electromagnetismin all

its splendor. They are:

Gauss' law. The electric flux through a closed surface is proportional

to the algebraic sum of electric charges contained within that closed

surface.

Gauss' law for magnetic fields. The magnetic flux through a closed

surface is zero; no magnetic charges exist.

Faraday's law. The line integral of the electric flux around a closed

curve is proportional to the instantaneous time rate of change of the

magnetic flux through a surface bounded by that closed curve.

Ampere's law, modified form. The line integral of the magnetic flux

around a closed curve is proportional to the sum of two terms: first, the

algebraic sum of electric currents flowing through that closed curve; and

second, the instantaneous time rate of change of the electric flux through

a surface bounded by that closed curve.

In addition to describing electromagnetism, his equations alsopredict

that waves can propagate through the electromagneticfield, and would always

propagate at the same speed -- these are electromagnetic waves.

Meissner effect (W. Meissner; 1933)

The decrease of the magnetic flux within a superconducting metalwhen it

is cooled below the critical temperature. That is,superconducting

materials reflect magnetic fields.

Michelson-Morley experiment (A.A. Michelson, E.W. Morley; 1887)

Possibly the most famous null-experiment of all time, designed toverify

the existence of the proposed "lumeniferous aether" throughwhich light

waves were thought to propagate. Since the Earthmoves through this aether,

a lightbeam fired in the Earth'sdirection of motion would lag behind one

fired sideways, where noaether effect would be present. This difference

could be detectedwith the use of an interferometer.

The experiment showed absolutely no aether shift whatsoever,where one

should have been quite detectable. Thus the aetherconcept was discredited

as was the constancy of the speed oflight.

Millikan oil drop experiment (R.A. Millikan)

A famous experiment designed to measure the electronic charge.Drops of

oil were carried past a uniform electric field betweencharged plates.

After charging the drop with x-rays, he adjustedthe electric field between

the plates so that the oil drop wasexactly balanced against the force of

gravity. Then the charge onthe drop would be known. Millikan did this

repeatedly and foundthat all the charges he measured came in integer

multiples only ofa certain smallest value, which is the charge on the

electron.

Newton's law of universal gravitation (Sir I. Newton)

Two bodies attract each other with equal and opposite forces;

themagnitude of this force is proportional to the product of the twomasses

and is also proportional to the inverse square of thedistance between the

centers of mass of the two bodies.

Newton's laws of motion (Sir I. Newton)

Newton's first law of motion. A body continues in its state of rest or

of uniform motion unless it is acted upon by an external force.

Newton's second law of motion. For an unbalanced force acting on a

body, the acceleration produces is proportional to the force impressed; the

constant of proportionality is the inertial mass of the body.

Newton's third law of motion. In a system where no external forces are

present, every action is always opposed by an equal and opposite reaction.

Ohm's law (G. Ohm; 1827)

The ratio of the potential difference between the ends of aconductor to

the current flowing through it is constant; theconstant of proportionality

is called the resistance, and isdifferent for different materials.

Olbers' paradox (H. Olbers; 1826)

If the Universe is infinite, uniform, and unchanging then theentire sky

at night would be bright -- about as bright as the Sun.The further you

looked out into space, the more stars there wouldbe, and thus in any

direction in which you looked your line-of-sight would eventually impinge

upon a star. The paradox isresolved by the Big Bang theory, which puts

forth that theUniverse is not infinite, non-uniform, and changing.

Pascal's principle

Pressure applied to an enclosed imcompressible static fluid

istransmitted undiminished to all parts of the fluid.

Paschen series

The series which describes the emission spectrum of hydrogen whenthe

electron is jumping to the third orbital. All of the linesare in the

infrared portion of the spectrum.

Pauli exclusion principle (W. Pauli; 1925)

No two identical fermions in a system, such as electrons in anatom, can

have an identical set of quantum numbers.

Peltier effect (J.C.A. Peltier; 1834)

The change in temperature produced at a junction between twodissimilar

metals or semiconductors when an electric currentpasses through the

junction.

permeability of free space; magnetic constant; m 0

The ratio of the magnetic flux density in a substance to theexternal

field strength for vacuum. It is equal to 4 p . 10-7 H/m.

permittivity of free space; electric constant; e0

The ratio of the electric displacement to the intensity of theelectric

field producing it in vacuum. It is equal to 8.854.10-12 F/m.

Pfund series

The series which describes the emission spectrum of hydrogen whenthe

electron is jumping to the fifth orbital. All of the linesare in the

infrared portion of the spectrum.

Photoelectric effect

An effect explained by A. Einstein that demonstrate that lightseems to

be made up of particles, or photons. Light can exciteelectrons (called

photoelectrons) to be ejected from a metal.Light with a frequency below a

certain threshold, at anyintensity, will not cause any photoelectrons to be

emitted fromthe metal. Above that frequency, photoelectrons are emitted

inproportion to the intensity of incident light. The reason is that a

photon has energy in proportion to itswavelength, and the constant of

proportionality is Planck'sconstant. Below a certain frequency -- and thus

below a certainenergy -- the incident photons do not have enough energy to

knockthe photoelectrons out of the metal. Above that threshold

energy,called the workfunction, photons will knock the photoelectrons outof

the metal, in proportion to the number of photons (theintensity of the

light). At higher frequencies and energies, thephotoelectrons ejected

obtain a kinetic energy corresponding tothe difference between the photon's

energy and the workfunction.

Planck constant; h

The fundamental constant equal to the ratio of the energy of aquantum

of energy to its frequency. It is the quantum of action.It has the value

6.626196.10-34 J.s.

Planck's radiation law

A law which more accurately described blackbody radiation becauseit

assumed that electromagnetic radiation is quantized.

Poisson spot (S.D. Poisson)

See Arago spot. Poisson predicted the existence of such a spot,and

actually used it to demonstrate that the wave theory of lightmust be in

error.

Principle of causality

The principle that cause must always preceed effect. Moreformally, if

an event A ("the cause") somehow influences an eventB ("the effect") which

occurs later in time, then event B cannotin turn have an influence on event

A. The principle is best illustrated with an example. Say thatevent A

constitutes a murderer making the decision to kill hisvictim, and that

event B is the murderer actually committing theact. The principle of

causality puts forth that the act ofmurder cannot have an influence on the

murderer's decision tocommit it. If the murderer were to somehow see

himself committingthe act and change his mind, then a murder would have

beencommitted in the future without a prior cause (he changed hismind).

This represents a causality violation. Both time traveland faster-than-

light travel both imply violations of causality,which is why most

physicists think they are impossible, or atleast impossible in the general

sense.

Principle of determinism

The principle that if one knows the state to an infinite accuracyof a

system at one point in time, one would be able to predict thestate of that

system with infinite accuracy at any other time,past or future. For

example, if one were to know all of thepositions and velocities of all the

particles in a closed system,then determinism would imply that one could

then predict thepositions and velocities of those particles at any other

time.This principle has been disfavored due to the advent of

quantummechanics, where probabilities take an important part in theactions

of the subatomic world, and the Heisenberg uncertaintyprinciple implies

that one cannot know both the position andvelocity of a particle to

arbitrary precision.

Rayleigh criterion; resolving power

A criterion for the how finely a set of optics may be able

todistinguish. It begins with the assumption that central ring ofone image

should fall on the first dark ring of the other.relativity principle;

principle of relativity

Rydberg formula

A formula which describes all of the characteristics of

hydrogen'sspectrum, including the Balmer, Lyman, Paschen, Brackett,

andPfund series.

Schroedinger's cat (E. Schroedinger; 1935)

A thought experiment designed to illustrate the counterintuitiveand

strange notions of reality that come along with quantummechanics.

A cat is sealed inside a closed box; the cat has ample air,food, and

water to survive an extended period. This box isdesigned so that no

information (i.e., sight, sound, etc.) canpass into or out of the box --

the cat is totally cut off fromyour observations. Also inside the box with

the poor kitty(apparently Schroedinger was not too fond of felines) is a

phialof a gaseous poison, and an automatic hammer to break it, floodingthe

box and killing the cat. The hammer is hooked up to a Geigercounter; this

counter is monitoring a radioactive sample and isdesigned to trigger the

hammer -- killing the cat -- should aradioactive decay be detected. The

sample is chosen so thatafter, say, one hour, there stands a fifty-fifty

chance of a decayoccurring.

The question is, what is the state of the cat after that onehour has

elapsed? The intuitive answer is that the cat is eitheralive or dead, but

you don't know which until you look. But it is one of them. Quantum

mechanics, on the other hands, saysthat the wavefunction describing the cat

is in a superposition ofstates: the cat is, in fact, fifty per cent alive

and fifty percent dead; it is both. Not until one looks and "collapses

thewavefunction" is the Universe forced to choose either a live cator a

dead cat and not something in between.

This indicates that observation also seems to be an importantpart of

the scientific process -- quite a departure from theabsolutely objective,

deterministic way things used to be withNewton.

Schwarzchild radius

The radius that a spherical mass must be compressed to in order

totransform it into a black hole; that is, the radius of compressionwhere

the escape velocity at the surface would reach lightspeed.

Snell's law; law of refraction

A relation which relates the change in incidence angle of awavefront

due to refraction between two different media.

Speed of light in vacuo

One of the postulates of A. Einstein's special theory ofrelativity,

which puts forth that the speed of light in vacuum --often written c, and

which has the value 299 792 458 m/s -- ismeasured as the same speed to all

observers, regardless of theirrelative motion. That is, if I'm travelling

at 0.9 c away fromyou, and fire a beam of light in that direction, both you

and Iwill independently measure the speed of that beam as c. One of the

results of this postulate (one of the predictionsof special relativity is

that no massive particle can beaccelerated to (or beyond) lightspeed, and

thus the speed of lightalso represents the ultimate cosmic speed limit.

Only masslessparticles (photons, gravitons, and possibly neutrinos, should

theyindeed prove to be massless) travel at lightspeed, and all

otherparticles must travel at slower speeds.

Spin-orbit effect

An effect that causes atomic energy levels to be split becauseelectrons

have intrinsic angular momentum (spin) in addition totheir extrinsic

orbital angular momentum.

Static limit

The distance from a rotating black hole where no observer canpossibly

remain at rest (with respect to the distant stars)because of inertial frame

dragging.

Stefan-Boltzmann constant; sigma (Stefan, L. Boltzmann)

The constant of proportionality present in the Stefan-Boltzmannlaw. It

is equal to

Stefan-Boltzmann law (Stefan, L. Boltzmann)

The radiated power (rate of emission of electromagnetic energy) ofa hot

body is proportional to the emissivity, an efficiencyrating, the radiating

surface area, and the fourth power of thethermodynamic temperature. The

constant of proportionality is theStefan-Boltzmann constant.

Stern-Gerlach experiment (O. Stern, W. Gerlach; 1922)

An experiment that demonstrates the features of spin (intrinsicangular

momentum) as a distinct entity apart from orbital angularmomentum.

Superconductivity

The phenomena by which, at sufficiently low temperatures, aconductor

can conduct charge with zero resistance.

Superfluidity

The phenomena by which, at sufficiently low temperatures, a fluidcan

flow with zero viscosity.

Superposition principle of forces

The net force on a body is equal to the sum of the forcesimpressed upon

it.

Superposition principle of states

The resultant quantum mechnical wavefunction due to two or

moreindividual wavefunctions is the sum of the individualwavefunctions.

Superposition principle of waves

The resultant wave function due to two or more individual wavefunctions

is the sum of the individual wave functions.

Thomson experiment; Kelvin effect (Sir W. Thomson [later Lord Kelvin])

When an electric current flows through a conductor whose ends

aremaintained at different temperatures, heat is released at a

rateapproximately proportional to the product of the current and

thetemperature gradient.

Twin paradox

One of the most famous "paradoxes" in history, predicted by

A.Einstein's special theory of relativity. Take two twins, born onthe same

date on Earth. One, Albert, leaves home for a triparound the Universe at

very high speeds (very close to that oflight), while the other, Henrik,

stays at home at rests. Specialrelativity predicts that when Albert

returns, he will find himselfmuch younger than Henrik. That is actually

not the paradox. The paradox stems fromattempting to naively analyze the

situation to figure out why.From Henrik's point of view (and from everyone

else on Earth),Albert seems to speed off for a long time, linger around,

and thenreturn. Thus he should be the younger one, which is what we

see.But from Albert's point of view, it's Henrik (and the whole of the

Earth) that are travelling, not he. According to specialrelativity, if

Henrik is moving relative to Albert, then Albertshould measure his clock as

ticking slower -- and thus Henrik isthe one who should be younger. But

this is not what happens.

So what's wrong with our analysis? The key point here is thatthe

symmetry was broken. Albert did something that Henrik didnot -- Albert

accelerated in turning around. Henrik did noaccelerating, as he and all

the other people on the Earth canattest to (neglecting gravity). So Albert

broke the symmetry, andwhen he returns, he is the younger one.

Ultraviolet catastrophe

A shortcoming of the Rayleigh-Jeans formula, which attempted todescribe

the radiancy of a blackbody at various frequencies of theelectromagnetic

spectrum. It was clearly wrong because as thefrequency increased, the

radiancy increased without bound;something quite not observed; this was

dubbed the "ultravioletcatastrophe." It was later reconciled and explained

by theintroduction of Planck's radiation law.

Universal constant of gravitation; G

The constant of proportionality in Newton's law of universalgravitation

and which plays an analogous role in A. Einstein'sgeneral relativity. It

is equal to 6.664.10-11 N.m2/kg2.

Van der Waals force (J.D. van der Waals)

Forces responsible for the non-ideal behavior of gases, and forthe

lattice energy of molecular crystals. There are three causes:dipole-dipole

interaction; dipole-induced dipole moments; anddispersion forces arising

because of small instantaneous dipolesin atoms.

Wave-particle duality

The principle of quantum mechanics which implies that light

(and,indeed, all other subatomic particles) sometimes act like a wave,and

sometime act like a particle, depending on the experiment youare

performing. For instance, low frequency electromagneticradiation tends to

act more like a wave than a particle; highfrequency electromagnetic

radiation tends to act more like aparticle than a wave.

Widenmann-Franz law

The ratio of the thermal conductivity of any pure metal to

itselectrical conductivity is approximately constant for any

giventemperature. This law holds fairly well except at lowtemperatures.

Wien's displacement law

For a blackbody, the product of the wavelength corresponding tothe

maximum radiancy and the thermodynamic temperature is aconstant. As a

result, as the temperature rises, the maximum ofthe radiant energy shifts

toward the shorter wavelength (higherfrequency and energy) end of the

spectrum.

Woodward-Hoffmann rules

Rules governing the formation of products during certain types

oforganic reactions.

Young's experiment; double-slit experiment (T. Young; 1801)

A famous experiment which shows the wave nature of light (andindeed of

other particles). Light is passed from a small sourceonto an opaque screen

with two thin slits. The light is refractedthrough these slits and

develops an interference pattern on theother side of the screen.

Zeeman effect; Zeeman line splitting (P. Zeeman; 1896)

The splitting of the lines in a spectrum when the source is exposed to

a magnetic field.

Used Literature.

«Basic Postulats» by Gabrele O’Hara

«Elementary Physic For Students» by Bill Strong

«Atomic Physic» by Steve Grevesone

«Optica» by Steve Grevesone

«Thermodynamic’s Laws» by Kay Fedos

-----------------------

380 622 . 10-23 J

K.

4.10-14 J

m3.

Km .

s.Mpc

J .

K.mol

5.6697.10-8 W

m2.K4.

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