Qhov hluav taws xob tam sim no yog dab tsi? Kev nco qab thawj zaug, txhais li cas tam sim no peb tau kawm?

Yooj yim yooj yim, qhov taw qhia txav ntawm cov khoom siv hluav taws xob hauv tus neeg xyuas pib yog hluav taws xob tam sim no.

Tsuas yog thaum ib yam khoom tau them cov khoom uas tuaj yeem txav tau yooj yim, nws tuaj yeem xa hluav taws xob tam sim no – uas yog, ua hluav taws xob. Cov khoom them nqi no uas koom nrog hauv kev coj ua yog hu ua cov cab kuj. Rau cov hlau, piv txwv li, tsuas yog sab nrauv electrons ntawm atoms tuaj yeem ua tus nqa khoom.

Qhov “kev taw qhia txav” hauv lub ntsiab lus ntawm hluav taws xob tam sim no feem ntau to taub yuam kev. Ntau tus neeg xav tias nws hais txog kev txav mus los nrog qee qhov kev taw qhia, tsis yog! Puas yog qhov kev taw qhia ntawm kev txav ntawm cov electrons hauv AC Circuit Court hloov?

Qhov tseeb, orienteering yog txheeb ze rau “random txav”!

Txij li cov electrons yog microscopic hais, lawv yuav tsum nyob rau hauv thermal txav txhua lub sijhawm. Thermal motion yog ib qho random motion, raws li qhia hauv daim duab hauv qab no.

This movement is actually very fast. For example, in metals at room temperature, the speed of electronic thermal movement is on the order of hundreds of kilometers per second!

Yog tias koj saib ze ntawm qhov kev txav mus los no, koj yuav pom tias cov kev taw qhia ntawm kev txav ntawm txhua qhov yog random txhua lub sijhawm. Yog tias koj ntxiv qhov nrawm vectors ntawm cov khoom no, qhov tshwm sim yuav luag xoom.

Now add an electric field to the conductor, and the electron superimposes a directional movement on the basis of random movement. Assuming that the electric field is to the left for a certain period of time, the movement of the electrons looks like the following. The red balls represent metal atoms on the crystal lattice, and the fast moving dots represent free electrons.

Nws puas zoo li ceev? Qhov ntawd yog vim hluav taws xob txav ceev heev! Tab sis qhov tseeb, random tsab ntawv tsa suab, uas tso nyiaj rau ib tug loj feem ntawm nws, tsis pab rau tam sim no. Thaum lub random tsab ntawv tsa suab raug tshem tawm, tus so yog zoo li qhov qeeb saib hauv qab no.

Qhov tseeb, qhov taw qhia txav ntawm electrons yog qeeb dua li qhov ceev ntawm thermal txav. Qhov “sib tsoo” txav ntawm electrons yog hu ua drift, lossis “drift”. Qee zaum, electrons yuav khiav mus rau qhov sib txawv vim kev sib tsoo nrog atoms. Tab sis feem ntau, electrons txav mus rau hauv ib qho kev taw qhia.

Yog hais tias lub teb hluav taws xob hloov cov kev taw qhia, cov kev taw qhia ntawm electron drift kuj yuav hloov.

Yog li ntawd, hom kev taw qhia kev txav no txhais tau hais tias qhov sib npaug ntawm qhov nrawm ntawm tag nrho cov electrons uas koom nrog hauv kev coj ua ntawm ib lub sijhawm tsis yog xoom, tab sis feem ntau yog nyob rau hauv ib qho kev taw qhia. Qhov kev taw qhia no tuaj yeem hloov tau txhua lub sijhawm, thiab qhov ntawd yog qhov hloov pauv tam sim no.

Therefore, current is not so much the “directional movement” of electric charge as it is the “collective movement” of electric charge.

Qhov loj ntawm qhov tam sim no nyob rau hauv tus neeg xyuas pib yog qhia los ntawm qhov kev siv tam sim no. Qhov kev siv tam sim no txhais tau tias yog tus nqi hluav taws xob dhau los ntawm ntu ntu ntawm tus neeg xyuas pib hauv ib lub sijhawm, uas yog

Peb tau kawm qee qhov ntau ntawm lub cev uas muaj lo lus “kev siv”, xws li kev siv hluav taws xob thiab kev sib nqus induction. Lawv feem ntau sawv cev rau kev faib ib lub sij hawm, chav tsev (los yog chav tsev ntim, lub kaum sab xis). Txawm li cas los xij, lo lus “kev siv zog” hauv qhov kev siv tam sim no tsis cuam tshuam txog qhov kev faib tawm tam sim no ntawm thaj chaw.

Qhov tseeb, lwm qhov ntau ntawm lub cev yog lub luag haujlwm rau kev faib tawm tam sim no mus rau cheeb tsam, uas yog qhov ceev tam sim no.

Txij li cov ntsiab lus ntawm cov hluav taws xob tam sim no yog qhov kev taw qhia ntawm lub zog hluav taws xob, yuav tsum muaj kev sib raug zoo ntawm kev siv tam sim no thiab kev nrawm nrawm!

Txhawm rau kom tau txais qhov kev sib raug zoo no, peb yuav tsum xub qhia meej txog lub tswv yim-cov neeg nqa khoom concentration, uas yog, tus naj npawb ntawm cov cab kuj nyob rau hauv ib chav tsev ntim, uas tau hais los ntawm .

Nws yog assumed tias tus neeg xyuas pib hla ntu yog, tus cab kuj concentration yog, lub drift tshaj tawm yog, thiab tus nqi them yog.

Then the charge in the conductor on the left side of the surface is, and these charges will pass through the surface within a certain period of time, so

Qhov no yog ib qho kev nthuav qhia microscopic ntawm kev siv tam sim no.

Tam sim no qhov ntom ntom yog qhov sib faib ntawm qhov tam sim no mus rau cheeb tsam, yog li qhov loj ntawm qhov ceev tam sim no, tab sis nws txhais tau tias yog vector, thiab cov kev taw qhia yog cov kev taw qhia ntawm drift velocity vector ntawm cov cab kuj zoo, yog li lub drift ntawm electrons nyob rau hauv lub hlau tuaj yeem tau txais los ntawm qhov nrawm, ua piv txwv hauv qab no.

Xav txog ib lub xov tooj tooj liab, xav tias txhua lub atom tooj liab txhawb nqa ib qho hluav taws xob ua tus nqa khoom. Muaj 1 mol ntawm tooj liab, nws ntim yog, molar mass yog, ceev yog, ces cov cab kuj concentration ntawm tooj liab hlau yog

Avogadro nyob qhov twg. Qhov ntom ntawm tooj liab yog pom, thiab tus nqi tau los ntawm kev hloov pauv yog hais txog chav tsev / cubic meter.

Assuming that the radius of the copper wire is 0.8mm, the current flowing is 15A, =1.6 C, and the drift velocity of electrons is calculated as

Nws tuaj yeem pom tias qhov drift ceev ntawm electrons yog qhov tsawg heev.

Rau cov neeg uas kawm circuits, saum toj no yog tag nrho cov ntsiab lus ntawm tam sim no.

Tab sis hauv physics, cov lus txhais saum toj no ntawm tam sim no tsuas yog lub ntsiab lus nqaim xwb. Ntau qhov tam sim no tsis txwv rau cov neeg siv hluav taws xob, tsuav yog qhov txav ntawm cov nqi hluav taws xob tam sim no. Piv txwv li, thaum lub electrons ntawm hydrogen atom txav ib ncig ntawm lub nucleus, ib qho hluav taws xob tam sim no yog tsim nyob rau hauv nws orbit.

Piv txwv tias tus nqi hluav taws xob yog thiab lub sijhawm txav mus los. Tom qab ntawd txhua lub sij hawm uas elapses, muaj xws li ib tug loj npaum li cas ntawm tus nqi dhau los ntawm ib qho kev hla ntawm lub voj, yog li qhov kev siv tam sim no yog nyob ntawm qhov kev sib raug zoo ntawm lub sij hawm, zaus thiab qhov nrawm nrawm, thiab qhov tam sim no kuj tseem tuaj yeem qhia tau tias yog

Piv txwv li, ib tug them hlau disk, rotating nyob ib ncig ntawm nws axis, kuj ua voj tam sim no nrog txawv radii.

Hom tam sim no tsis yog ib qho kev coj ua tam sim no thiab tsis tuaj yeem tsim hluav taws xob Joule! Tsis tuaj yeem tsim lub voj voog tiag tiag.

Txwv tsis pub, koj puas muab rau kuv xam seb yuav ua li cas joule cua sov yog generated ib ob los ntawm cov electrons ntawm hydrogen atom?

In fact, the current in vacuum does not satisfy Ohm’s law. Because, for the electric current formed by the movement of charged particles in the vacuum, the carriers are not collided similar to the lattice in the metal, so the vacuum has no resistance and no conductance.

Lub zog ntawm cov nqi hluav taws xob tsim hluav taws xob tam sim no, thiab cov nqi hluav taws xob nws tus kheej ua rau lub zog hluav taws xob. Qhov no yooj yim ua rau muaj kev nkag siab yuam kev. Ntau tus neeg yog li xav tias hluav taws xob teb ntawm cov khoom siv hluav taws xob uas tsim hluav taws xob yuav tsum raug nthuav tawm. Tab sis qhov tseeb, rau cov conduction tam sim no nyob rau hauv ib tug dav neeg xyuas pib, cov cab kuj ntws nyob rau hauv ib tug keeb kwm yav dhau los ntawm ib tug loj tus naj npawb ntawm zoo nqi hlau ions, thiab tus neeg xyuas pib nws tus kheej yog nruab nrab!

Peb feem ntau hu ua qhov tshwj xeeb tam sim no “sib npaug tam sim no”. Qhov sib npaug ntawm no txhais tau hais tias nws tsim ib qho chaw sib nqus ntawm tib lub hauv paus raws li qhov sib txawv tam sim no!

Reminder: Do not confuse the “equivalent current” here with the “equivalent circuit” in circuit analysis

Qhov tseeb, thaum peb xub kawm txog qhov sib nqus, cov hluav taws xob tam sim no hauv Biot-Saffar txoj cai yog cov hluav taws xob dav dav uas muaj qhov sib npaug tam sim no. Tau kawg, qhov conduction tam sim no hauv Maxwell qhov sib npaug kuj yog hais txog qhov tam sim no dav dav.

Cov neeg uas tau kawm txog cov nyhuv photoelectric paub tias thaum lub photoelectron drifts los ntawm cathode mus rau lub anode, yog hais tias lub zog ntawm huab cua tsis quav ntsej, qhov tam sim no yog tshwm sim los ntawm lub zog ntawm hluav taws xob nqi nyob rau hauv lub nqus tsev vacuum, thiab tsis muaj kev tiv thaiv, yog li ntawd nws yog tsim nyog. tsis txwv los ntawm Ohm txoj cai.

Yog li, qhov no puas yog tib yam hais txog hluav taws xob tam sim no hauv physics?

Tsis muaj! Kuj tseem muaj ob hom, xws li magnetizing tam sim no thiab kev hloov tam sim no.

Lawv kuj yog ob qhov sib npaug tam sim no, uas, raws li lub npe qhia, kuj tau qhia los piav qhia cov hlau nplaum. Hauv lwm lo lus, lawv tau tawg tawm ntawm cov yam ntxwv tseem ceeb ntawm “kev txav mus los” tam sim no!

Qhov ntawd yog amazing! Tsis muaj hluav taws xob txav txav, yog vim li cas nws thiaj li hu ua hluav taws xob tam sim no?

Tsis txhob txhawj, thiab maj mam mloog kuv hais.

Cia peb saib cov magnetizing tam sim no ua ntej.

Nws tau pom tias cov hlau nplaum yog tshwm sim los ntawm kev txav ntawm hluav taws xob (tsis xav txog qhov kev piav qhia ntawm cov hlau nplaum los ntawm cov khoom siv hauv nruab nrab ntawm kev sib tw rau lub sijhawm). Nyob rau hauv thiaj li yuav piav txog tej yam ntuj tso magnetism, Fabkis physicist Ampere muab tso rau pem hauv ntej lub hypothesis ntawm “molecular ncig”.

As shown in the figure below, any atom or molecule can be regarded as having an electric charge rotating around the center, forming a tiny loop current, that is, “molecular circulation”.

Raws li txoj cai lij choj hais tias cov hluav taws xob tam sim no excites lub magnetic teb, lub molecular ncig yuav tsim ib tug ntau ntawm lub cev hu ua magnetic moment. Nws qhov loj me yog thaj chaw uas nyob ze los ntawm cov molecular ncig multiplied los ntawm qhov sib npaug tam sim no ntawm molecular ncig, thiab nws cov kev taw qhia yog nyob rau hauv txoj cai-tes kauv kev sib raug zoo nrog cov kev taw qhia ntawm kev ncig, uas yog.

Obviously, cov kev taw qhia ntawm lub sij hawm sib nqus yog raws nraim li cov kev taw qhia ntawm lub magnetic teb tsim los ntawm lub circulating tam sim no.

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Under normal circumstances, the arrangement of the molecular circulation of a substance is chaotic, so the substance is not magnetic, as shown on the left side of the figure below. When subjected to an external magnetic field, these molecular circulations will be approximately neatly arranged. As shown on the right side of the figure below, their magnetic moments are arranged in one direction as much as possible, just like countless small magnetic needles gathered together to form a total magnetic field, and the whole material composed of them becomes magnetic.

Suppose there is a cylindrical magnet, the inner molecular circulation is neatly arranged, and the sections of each molecular circulation at the edge of the magnet section are connected together to form a large circulation, as shown in the figure below.

Raws li qhov no, peb tuaj yeem xav tias bar hlau nplaum zoo li lub zog solenoid. Hauv lwm lo lus, muaj qhov pom tsis pom tam sim no nyob rau saum npoo ntawm cov hlau nplaum! Hom tam sim no tsis tuaj yeem txuas thiab siv tau. Nws yog nyob rau saum npoo ntawm cov hlau nplaum. Peb hu nws “binding tam sim no” lossis “magneticizing tam sim no”.

Yog li ntawd, cov hlau nplaum tam sim no yog tam sim no, vim tias nws yog tib yam li tam sim no tsim los ntawm kev txav ntawm cov nqi hluav taws xob tiag tiag, uas muaj peev xwm sib npaug ua kom muaj qhov sib nqus!

Cia peb saib qhov kev hloov pauv tam sim no dua.

According to the Ampere’s loop theorem, the integral of the magnetic field strength on a closed path is equal to the flux of the current density on any curved surface bounded by this path, that is, this theorem is called Stokes’ theorem in mathematics. It tells us that the integral of a vector along any closed path must be equal to the flux of its curl (here) to any surface bounded by the closed path.

Txij li thaum nws yog lej theorem, nws yuav tsum yog qhov tseeb, vim hais tias kev ua lej yog qhov kev xav tau raws li axioms.

Yog li ntawd, Ampere Loop Theorem yuav tsum tuav txhua lub sijhawm!

Txawm li cas los xij, tus kws tshaj lij Scottish physicist Maxwell tau pom tias thaum ntsib nrog qhov tsis ruaj khov tam sim no, Ampere voj theorem yog qhov tsis sib xws.

The typical unstable current occurs during the charging and discharging of the capacitor. As shown in the figure below, there is an unstable current during the short period of capacitor charging.

Tab sis lub Circuit Court yog disconnected ntawm lub capacitor daim hlau, uas yuav ua rau muaj teeb meem loj.

Piv txwv li peb xav txog ib txoj hauv kev kaw uas hla cov hlau, raws li qhia hauv daim duab hauv qab no, lub voj voog cim C, thiab nkhaus nto nrog nws raws li tus ciam teb tuaj yeem xaiv arbitrarily. Nyob rau hauv daim duab, lub voj voog ncig ntawm C nws tus kheej thiab hla lub capacitor raug xaiv. Qhov nkhaus ntawm sab laug phaj.

Raws li qhov chaw ncig, nws tuaj yeem pom tau tias raws li qhov nkhaus ntawm qhov chaw, tab sis raws li lub voj voog sib nqus ntawm lub zog sib nqus, nws cov nqi yuav tsum tau txiav txim siab!

Yuav ua li cas?

Maxwell ntseeg hais tias Ampere lub voj theorem yuav tsum raug tsim. Tam sim no muaj teeb meem, nws yuav tsum yog vim ib feem ntawm tam sim no tsis tau pom los ntawm peb ua ntej, tab sis nws muaj!

Yog li, yuav ua li cas thiaj nrhiav tau ib feem ntawm qhov tam sim no?

Txij li qhov teeb meem nyob nruab nrab ntawm daim hlau, pib los ntawm nruab nrab ntawm daim hlau.

Los ntawm kev txheeb xyuas, Maxwell pom tias tsis hais txog kev them nqi lossis kev tso tawm, muaj lub cev muaj nuj nqis ntawm cov phaj capacitor txhua lub sijhawm uas tau sib txuas nrog qhov loj thiab cov kev taw qhia ntawm qhov tam sim no. Nws yog lub sij hawm derivative ntawm flux ntawm hluav taws xob xaav vector, uas yog, nws yog txhais raws li qhov kev hloov tam sim no.

Yog tias nws tau txiav txim siab tias qhov no yog ib feem ntawm qhov tam sim no uas tsis tau pom ua ntej, ces tam sim no tag nrho yog tam sim no. Qhov ntawd yog hais tias, txawm hais tias lub voj voog ntawm cov phiaj yog txiav tawm, qhov kev sib txuas ntawm cov hluav taws xob xaim hluav taws xob thiab cov sum ntawm cov tam sim no ua ke, tag nrho, kom ntseeg tau qhov txuas ntxiv ntawm qhov tam sim no txhua lub sijhawm.

Yuav rov qab mus rau yav tas los contradiction, peb tam sim no paub hais tias, raws li cov uas yuav tsum tau ntawm Stokes ‘theorem, thaum xam xyuas cov flux ntawm tam sim no ceev rau ib tug qhov chaw kaw, cov kev ceev ntawm xaav tam sim no yuav tsum tau raug xam tias yog, uas yog, kom ampere voj Txoj kev xav yog li ntawd, Los ntawm “kev tshawb pom” cov khoom tam sim no tshiab, qhov teebmeem ntawm Ampere Loop Theorem raug daws!

Yog vim li cas vim li cas “kev taw qhia” tsis siv ntawm no, tab sis “discovery” yog siv ntawm no. Qhov kuv xav hais txog yog qhov tam sim no tsis yog kev them nyiaj ua lej, tab sis yog qhov tseeb, tab sis nws tsis tau pom ua ntej.

Vim li cas nws muaj nyob hauv thawj qhov chaw? Vim tias nws ua raws li cov hluav taws xob tam sim no, zoo li cov khoom siv hluav taws xob, nws ua rau lub zog sib nqus sib npaug, tshwj tsis yog tias tsis muaj kev txav ntawm hluav taws xob, tsis tas yuav tsum tau xaim, thiab tsis muaj hluav taws xob Joule tuaj yeem tsim tawm, yog li nws tau raug tsis quav ntsej!

Tab sis nws yeej tshwm sim los ntawm nws tus kheej, cia li khaws ib qho profile tsawg, nws tau ua ntsiag to txaus siab rau qhov chaw sib nqus nyob ntawd txhua lub sijhawm!

Hauv lwm lo lus, thaum peb ntsib qhov chaw sib nqus, lub ntsiab lus tseem ceeb ntawm tam sim no nqaim dhau. Lub ntsiab ntawm hluav taws xob tam sim no tsis yog lub zog ntawm hluav taws xob, nws yuav tsum yog ib yam dab tsi uas tuaj yeem ua rau muaj kev sib nqus.

Txog tam sim no, ob peb hom tam sim no tau qhia. Lawv txhua tus muaj nyob hauv lub hom phiaj, thiab qhov lawv muaj nyob hauv ib qho yog tias txhua qhov tam sim no tuaj yeem sib npaug sib npaug ntawm thaj chaw sib nqus.