Физические законы, переменные, принципы

Физические законы, переменные, принципы

Municipal Liceum № 57

Laws, rules, principles, effects, paradoxes, limits, constants, experiments, & thought-experiments in physics.

Pupil : Morozov Michael

Togliatti

1998
Ampere's law (A.M. Ampere)

The line integral of the magnetic flux around a closed curve isproportional to the algebraic sum of electric currents flowingthrough that closed curve. This was later modified to add a second term when it wasincorporated into Maxwell's equations.
Anthropic principle

Weak anthropic principle. The conditions necessary for the development of intelligent life will be met only in certain regions that are limited in space and time. That is, the region of the Universe in which we live is not necessarily representative of a purely random set of initial conditions; only those favorable to intelligent life would actually develop creatures who wonder what the initial conditions of the Universe were.

Strong anthropic principle. A more forceful argument that the weak principle: It states, rather straightforwardly, that if the laws of the
Universe were not conducive to the development of intelligent creatures to ask about the initial conditions of the Universe, intelligent life would never have evolved to ask the question in the first place. In other words, the laws of the Universe are the way they are because if they weren't, you would not be able to ask such a question.
Arago spot (D.F.J. Arago)

A bright spot that appears in the shadow of a uniform disc beingbacklit by monochromatic light emanating from a point source.
Archimedes' principle

A body that is submerged in a fluid is buoyed up by a force equalin magnitude to the weight of the fluid that is displaced, anddirected upward along a line through the center of gravity of thedisplaced fluid.
Atwood's machine

A weight-and-pulley system devised to measure the acceleration dueto gravity at Earth's surface by measuring the net acceleration ofa set of weights of known mass around a frictionless pulley.
Avogadro constant; L; NA (Count A. Avogadro; 1811)

The number of atoms or molecules in a sample of an idea gas whichis at standard temperature and pressure. It is equal to about 6.022 52.1023 mol-
1.
Avogadro's hypothesis (Count A. Avogadro; 1811)

Equal volumes of all gases at the same temperature and pressurecontain equal numbers of molecules. It is, in fact, only true forideal gases.
Balmer series (J. Balmer; 1885)

An equation which describes the emission spectrum of hydrogen whenan electron is jumping to the second orbital; four of the linesare in the visible spectrum, and the remainder are in theultraviolet.
Baryon decay

The theory, predicted by several grand-unified theories, that aclass of subatomic particles called baryons (of which the nucleons-- protons and neutrons -- are members) are not ultimately stablebut indeed decay.
Present theory and experimentation demonstratethat if protons are indeed unstable, they decay with a halflife ofat least 1034 y.
Bernoulli's equation

An equation which states that an irrotational fluid flowingthrough a pipe flows at a rate which is inversely proportional tothe cross-sectional area of the pipe. That is, if the pipeconstricts, the fluid flows faster; if it widens, the fluid flowsslower.
BCS theory (J. Bardeen, L.N. Cooper, J.R. Schrieffer; 1957)

A theory put forth to explain both superconductivity andsuperfluidity.
It suggests that in the superconducting (orsuperfluid) state electrons form
Cooper pairs, where two electronsact as a single unit. It takes a nonzero amount of energy tobreak such pairs, and the imperfections in the superconductingsolid (which would normally lead to resistance) are incapable ofbreaking the pairs, so no dissipation occurs and there is noresistance.

Biot-Savart law (J.B. Biot, F. Savart)

A law which describes the contributions to a magnetic field by anelectric current. It is analogous to Coulomb's law forelectrostatics.
Blackbody radiation

The radiation -- the radiance at particular frequencies all acrossthe spectrum -- produced by a blackbody -- that is, a perfectradiator (and absorber) of heat. Physicists had difficultyexplaining it until Planck introduced his quantum of action.
Bode's law

A mathematical formula which generates, with a fair amount ofaccuracy, the semimajor axes of the planets in order out from theSun. Write down the sequence 0, 3, 6, 12, 24, . . . and then add4 to each term. Then divide each term by 10. This is intended togive you the positions of the planets measured in astronomicalunits.

Bode's law had no theoretical justification when it was firstintroduced; it did, however, agree with the soon-to-be- discoveredplanet Uranus' orbit (19.2 au actual; 19.7 au predicted).Similarly, it predicted a missing planet betwen Mars and
Jupiter,and shortly thereafter the asteroids were found in very similarorbits (2.8 au actual for Ceres; 2.8 au predicted). However, theseries seems to skip over Neptune's orbit.
Bohr magneton (N. Bohr)

The quantum of magnetic moment.
Bohr radius (N. Bohr)

The distance corresponding the mean distance of an electron fromthe nucleus in the ground state.
Boltzmann constant; k (L. Boltzmann)

A constant which describes the relationship between temperatureand kinetic energy for molecules in an ideal gas. It is equal to1.

Boyle's law (R. Boyle; 1662); Mariotte's law (E. Mariotte; 1676)

The product of the pressure and the volume of an ideal gas atconstant temperature is a constant.
Brackett series (Brackett)

The series which describes the emission spectrum of hydrogen whenthe electron is jumping to the fourth orbital. All of the linesare in the infrared portion of the spectrum.
Bragg's law (Sir W.L. Bragg; 1912)

When a beam of x-rays strikes a crystal surface in which thelayers of atoms or ions are regularly separated, the maximumintensity of the reflected ray occurs when the sine of thecompliment of the angle of incidence is equal to an integermultiplied by the wavelength of x-rays divided by twice thedistance between layers of atoms or ions.
Brewster's law (D. Brewster)

The extent of the polarization of light reflected from atransparent surface is a maximum when the reflected ray is atright angles to the refracted ray.
Brownian motion (R. Brown; 1827)

The continuous random motion of solid microscopic particles whensuspended in a fluid medium due to the consequence of continuousbombardment by atoms and molecules.
Carnot's theorem (S. Carnot)

The theorem which states that no engine operating between twotemperatures can be more efficient than a reversible engine. centrifugal pseudoforce

A pseudoforce -- a fictitious force resulting from being in a non- inertial frame of reference -- that occurs when one is moving inuniform circular motion. One feels a "force" outward from thecenter of motion.
Chandrasekhar limit (S. Chandrasekhar; 1930)

A limit which mandates that no white dwarf (a collapsed,degenerate star) can be more massive than about 1.2 solar masses.Anything more massive must inevitably collapse into a neutronstar.
Charles' law (J.A.C. Charles; c. 1787)

The volume of an ideal gas at constant pressure is proportional tothe thermodynamic temperature of that gas.
Cherenkov radiation (P.A. Cherenkov)

Radiation emitted by a massive particle which is moving fasterthan light in the medium through which it is travelling. Noparticle can travel faster than light in vacuum, but the speed oflight in other media, such as water, glass, etc., are considerablylower. Cherenkov radiation is the electromagnetic analogue of thesonic boom, though Cherenkov radiation is a shockwave set up inthe electromagnetic field.
Complementarity principle (N. Bohr)

The principle that a given system cannot exhibit both wave-likebehavior and particle-like behavior at the same time. That is,certain experiments will reveal the wave-like nature of a system,and certain experiments will reveal the particle-like nature of asystem, but no experiment will reveal both simultaneously.
Compton effect (A.H. Compton; 1923)

An effect that demonstrates that photons (the quantum ofelectromagnetic radiation) have momentum. A photon fired at astationary particle, such as an electron, will impart momentum tothe electron and, since its energy has been decreased, willexperience a corresponding decrease in frequency.
Coriolis pseudoforce (G. de Coriolis; 1835)

A pseudoforce -- a fictitious force, like the centrifugal "force"-- which arises because the rotation of the Earth varies atdifferent latitutdes (maximum at the equator, zero at the poles). correspondence principle.

The principle that when a new, more specialized theory is putforth, it must reduce to the more general (and usually simpler)theory under normal circumstances. There are correspondenceprinciples for general relativity to special relativity andspecial relativity to Newtonian mechanics, but the most widelyknown correspondence principle (and generally what is meant whenone says "correspondence principle") is that of quantum mechanicsto classical mechanics.
Cosmic background radiation; primal glow

The background of radiation mostly in the frequency range 3.1011 to
3.108 Hz discovered in space in 1965. It is believedto be the cosmologically redshifted radiation released by the BigBang itself.
Presently it has an energy density in empty space ofabout
Cosmological redshift

An effect where light emitted from a distant source appearsredshifted because of the expansion of space itself. Compare withthe Doppler effect.
Coulomb's law

The primary law for electrostatics, analogous to Newton's law ofuniversal gravitation. It states that the force between two pointcharges is proportional to the algebraic product of theirrespective charges as well as proportional to the inverse squareof the distance between them.
CPT theorem
Curie-Weiss law (P. Curie, P.-E. Weiss)

A more general form of Curie's law, which states that thesusceptibility of a paramagnetic substance is inverselyproportional to the thermodynamic temperature of the substanceless the Weiss constant, a characteristic of that substance.
Curie's law (P. Curie)

The susceptibility of a paramagnetic substance is inverselyproportional to the thermodynamic temperature of the substance.The constant of proportionality is called the Curie constant.
Dalton's law of partial pressures (J. Dalton)

The total pressure of a mixture of ideal gases is equal to the sumof the partial pressures of its components; that is, the sum ofthe pressures that each component would exert if it were presentalone and occuped the same volume as the mixture.

Davisson-Germer experiment (C.J. Davisson, L.H. Germer; 1927)

An experiment that conclusively confirmed the wave nature ofelectrons; diffraction patterns were observed by an electron beampenetrating into a nickel target.
De Broglie wavelength (L. de Broglie; 1924)

The prediction that particles also have wave characteristics,where the effective wavelength of a particle would be inverselyproportional to its momentum, where the constant ofproportionality is the Planck constant.
Doppler effect (C.J. Doppler)

Waves emitted by a moving observer will be blueshifted(compressed) if approaching, redshifted (elongated) if receding.It occurs both in sound as well as electromagnetic phenomena,although it takes on different forms in each.
Dulong-Petit law (P. Dulong, A.T. Petit; 1819)

The molar heat capacity is approximately equal to the three timesthe gas constant.
Einstein-Podolsky-Rosen effect

Consider the following quantum mechanical thought-experiment:Take a particle which is at rest and has spin zero. Itspontaneously decays into two fermions (spin 0.5 particles), whichstream away in opposite directions at high speed. Due to the lawof conservation of spin, we know that one is a spin +0.5 and theother is spin -0.5. Which one is which? According to quantummechanics, neither takes on a definite state until it is observed(the wavefunction is collapsed).

The EPR effect demonstrates that if one of the particles isdetected, and its spin is then measured, then the other particle-- no matter where it is in the Universe -- instantaneously isforced to choose as well and take on the role of the otherparticle. This illustrates that certain kinds of quantuminformation travel instantaneously; not everything is limited bythe speed of light.

However, it can be easily demonstrated that this effect doesnot make faster-than-light communication possible.
Equivalence principle

The basic postulate of A. Einstein's general theory of relativity,which posits that an acceleration is fundamentallyindistinguishable from a gravitational field. In other words, ifyou are in an elevator which is utterly sealed and protected fromthe outside, so that you cannot "peek outside," then if you feel aforce (weight), it is fundamentally impossible for you to saywhether the elevator is present in a gravitational field, orwhether the elevator has rockets attached to it and isaccelerating
"upward."

The equivalence principle predicts interesting generalrelativistic effects because not only are the twoindistinguishable to human observers, but also to the Universe aswell, in a way -- any effect that takes place when an observer isaccelerating should also take place in a gravitational field, andvice versa.
Ergosphere

The region around a rotating black hole, between the event horizonand the static limit, where rotational energy can be extractedfrom the black hole.
Event horizon

The radius of surrounding a black hole at which a particle wouldneed an escape velocity of lightspeed to escape; that is, thepoint of no return for a black hole.
Faraday constant; F (M. Faraday)

The electric charge carried by one mole of electrons (or singly-ionized ions). It is equal to the product of the Avogadroconstant and the
(absolute value of the) charge on an electron; itis
9.648670.104 C/mol.
Faraday's law (M. Faraday)

The line integral of the electric flux around a closed curve isproportional to the instantaneous time rate of change of themagnetic flux through a surface bounded by that closed curve.
Faraday's laws of electrolysis (M. Faraday)
1. The amount of chemical change during electrolysis is proportional to the charge passed.

2. The charge required to deposit or liberate a mass is proportional to the charge of the ion, the mass, and inversely proprtional to the relative ionic mass. The constant of proportionality is the Faraday constant.
Faraday's laws of electromagnetic induction (M. Faraday)
1. An electromotive force is induced in a conductor when the magnetic field surrounding it changes.
2. The magnitude of the electromotive force is proportional to the rate of change of the field.

3. The sense of the induced electromotive force depends on the direction of the rate of the change of the field.
Fermat's principle; principle of least time (P. de Fermat)

The principle, put forth by P. de Fermat, states that the pathtaken by a ray of light between any two points in a system isalways the path that takes the least time.
Fermi paradox

E. Fermi's conjecture, simplified with the phrase, "Where arethey?" questioning that if the Galaxy is filled with intelligentand technological civilizations, why haven't they come to us yet?There are several possible answers to this question, but since weonly have the vaguest idea what the right conditions for life andintelligence in our Galaxy, it and Fermi's paradox are no morethan speculation.
Gauss' law (K.F. Gauss)

The electric flux through a closed surface is proportional to thealgebraic sum of electric charges contained within that closedsurface.
Gauss' law for magnetic fields (K.F. Gauss)

The magnetic flux through a closed surface is zero; no magneticcharges exist.
Grandfather paradox

A paradox proposed to discount time travel and show why itviolates causality. Say that your grandfather builds a timemachine. In the present, you use his time machine to go back intime a few decades to a point before he married his wife (yourgrandmother). You meet him to talk about things, and an argumentensues (presumably he doesn't believe that you're hisgrandson/granddaughter), and you accidentally kill him.

If he died before he met your grandmother and never hadchildren, then your parents could certainly never have met (one ofthem didn't exist!) and could never have given birth to you. Inaddition, if he didn't live to build his time machine, what areyou doing here in the past alive and with a time machine, if youwere never born and it was never built?
Hall effect

When charged particles flow through a tube which has both anelectric field and a magnetic field (perpendicular to the electricfield) present in it, only certain velocities of the chargedparticles are preferred, and will make it undeviated through thetube; the rest will be deflected into the sides. This effect isexploited in such devices as the mass spectrometer and in theThompson experiment. This is called the Hall effect.
Hawking radiation (S.W. Hawking; 1973)

The theory that black holes emit radiation like any other hotbody.
Virtual particle-antiparticle pairs are constantly beingcreated in supposedly empty space. Every once in a while, onewill be created in the vicinity of a black hole's event horizon.One of these particles might be catpured by the black hole,forever trapped, while the other might escape the black hole'sgravity. The trapped particle, which would have negative energy(by definition), would reduce the mass of the black hole, and theparticle which escaped would have positive energy. Thus, from adistant, one would see the black hole's mass decrease and aparticle escape the vicinity; it would appear as if the black holewere emitting radiation. The rate of emission has a negativerelationship with the mass of the black hole; massive black holesemit radiation relatively slowly, while smaller black holes emitradiation -- and thus decrease their mass -- more rapidly.

Heisenberg uncertainty principle (W. Heisenberg; 1927)

A principle, central to quantum mechanics, which states that themomentum (mass times velocity) and the position of a particlecannot both be known to infinite accuracy; the more you know aboutone, the lest you know about the other.

It can be illustrated in a fairly clear way as follows: Tosee something (let's say an electron), we have to fire photons atit, so they bounce off and come back to us, so we can "see" it.If you choose low- frequency photons, with a low energy, they donot impart much momentum to the electron, but they give you a veryfuzzy picture, so you have a higher uncertainty in position sothat you can have a higher certainty in momentum.
On the otherhand, if you were to fire very high-energy photons (x-rays orgammas) at the electron, they would give you a very clear pictureof where the electron is (high certainty in position), but wouldimpart a great deal of momentum to the electron (higheruncertainty in momentum). In a more generalized sense, the uncertainty principle tellsus that the act of observing changes the observed in fundamentalway.
Hooke's law (R. Hooke)

The stress applied to any solid is proportional to the strain itproduces within the elastic limit for that solid. The constant ofthat proportionality is the Young modulus of elasticity for thatsubstance.
Hubble constant; H0 (E.P. Hubble; 1925)

The constant which determines the relationship between thedistance to a galaxy and its velocity of recession due to theexpansion of the Universe.
It is not known to great accuracy, butis believed to lie between 49 and 95
Hubble's law (E.P. Hubble; 1925)

A relationship discovered between distance and radial velocity.The further away a galaxy is away from is, the faster it isreceding away from us. The constant of proportionality isHubble's constant, H0. The cause is interpreted as the expansionof space itself.
Huygens' construction; Huygens' principle (C. Huygens)

The mechanics propagation of a wave of light is equivalent toassuming that every point on the wavefront acts as point source ofwave emission.
Ideal gas constant; universal molar gas constant; R

The constant that appears in the ideal gas equation. It is equalto
8.314 34.
Ideal gas equation

An equation which sums up the ideal gas laws in one simpleequation. It states that the product of the pressure and thevolume of a sample of ideal gas is equal to the product of theamount of gas present, the temperature of the sample, and theideal gas constant.
Ideal gas laws

Boyle's law. The pressure of an ideal gas is inversely proportional to the volume of the gas at constant temperature.

Charles' law. The volume of an ideal gas is directly proportional to 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)

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