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)
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