Ohm Txoj Cai yog txoj cai yooj yim ntawm hluav taws xob circuits. Nyob rau tib lub sijhawm, nws tso cai rau peb piav qhia ntau yam xwm txheej ntuj. Piv txwv li, ib tug tuaj yeem nkag siab tias yog vim li cas hluav taws xob tsis "tua" cov noog uas zaum ntawm cov xov hlau. Rau physics, Ohm txoj cai yog qhov tseem ceeb heev. Yog tias tsis muaj nws txoj kev paub, nws yuav tsis tuaj yeem tsim hluav taws xob ruaj khov lossis yuav tsis muaj hluav taws xob txhua.
Kev vam khom kuv=I(U) thiab nws tus nqi
keeb kwm ntawm kev tshawb pom ntawm cov khoom siv tiv thaiv yog ncaj qha ntsig txog cov yam ntxwv tam sim no-voltage. Nws yog dab tsi? Cia peb ua ib lub voj voog uas muaj hluav taws xob tas mus li thiab xav txog ib qho ntawm nws cov ntsiab lus: lub teeb, cov yeeb nkab roj, ib tus neeg xyuas pib hlau, lub hwj hluav taws xob, thiab lwm yam.
Hloov qhov voltage U (feem ntau hu ua V) muab rau lub ntsiab lus nug, peb yuav taug qab qhov kev hloov pauv ntawm lub zog tam sim no (I) dhau los ntawm nws. Raws li qhov tshwm sim, peb yuav tau txais kev vam khom ntawm daim ntawv I \u003d I (U), uas yog hu ua "voltage yam ntxwv ntawm lub caij" thiab yog qhov qhia ncaj qha ntawm nws.hluav taws xob khoom.
V/A tus yam ntxwv yuav zoo li txawv rau cov ntsiab lus sib txawv. Nws daim ntawv yooj yim tshaj plaws yog tau los ntawm kev txiav txim siab tus neeg xyuas pib hlau, uas tau ua los ntawm Georg Ohm (1789 - 1854).
Volt-ampere yam ntxwv yog kev sib raug zoo. Yog li ntawd, nws daim duab yog ib txoj kab ncaj nraim.
Txoj cai hauv nws daim ntawv yooj yim tshaj plaws
Ohm txoj kev tshawb fawb ntawm cov yam ntxwv tam sim no-voltage ntawm cov neeg xyuas pom tau pom tias lub zog tam sim no hauv cov hlau conductor yog proportional rau qhov sib txawv ntawm qhov kawg (I ~ U) thiab inversely proportional rau ib co coefficient, uas yog, kuv. ~ 1/R. Qhov coefficient no hu ua "conductor resistance", thiab chav ntsuas ntawm qhov hluav taws xob tsis kam yog Ohm lossis V / A.
Ib yam ntxiv. Ohm txoj cai feem ntau siv los xam cov kev tiv thaiv hauv circuits.
Law wording
Ohm Txoj Cai hais tias lub zog tam sim no (I) ntawm ib ntu ntawm Circuit Court yog proportional rau qhov voltage hauv seem no thiab inversely proportional rau nws resistance.
Nws yuav tsum tau muab sau tseg tias nyob rau hauv daim ntawv no txoj cai tseem muaj tseeb tsuas yog rau ib homogeneous seem ntawm cov saw. Homogeneous yog ib feem ntawm cov hluav taws xob hluav taws xob uas tsis muaj qhov tam sim no. Yuav siv Ohm txoj cai li cas hauv ib lub voj voog tsis sib xws yuav tau tham hauv qab no.
Tom qab ntawd, nws tau sim ua kom txoj cai tseem siv tau rau kev daws teeb meemelectrolytes nyob rau hauv ib qho hluav taws xob circuit.
Lub ntsiab lus ntawm kev tiv thaiv
Resistance yog ib yam khoom ntawm cov khoom, tshuaj los yog xov xwm los tiv thaiv kev kis ntawm hluav taws xob tam sim no. Quantitatively, ib tug tsis kam ntawm 1 ohm txhais tau hais tias nyob rau hauv ib tug neeg xyuas pib nrog ib tug voltage ntawm 1 V ntawm nws kawg, ib tug hluav taws xob tam sim no ntawm 1 A tuaj yeem dhau.
Hluav taws xob tiv taus
Kev sim, nws tau pom tias qhov tsis kam ntawm cov hluav taws xob tam sim no ntawm tus neeg xyuas pib nyob ntawm nws qhov ntev: ntev, dav, qhov siab. Thiab tseem ntawm nws cov duab (sphere, lub tog raj kheej) thiab cov khoom uas nws tau ua. Yog li, cov qauv rau kev tiv thaiv, piv txwv li, ntawm homogeneous cylindrical conductor yuav yog: R \u003d pl / S.
Yog hais tias hauv cov qauv no peb muab s=1 m 2 thiab l=1 m, ces R yuav tus lej sib npaug rau p. Los ntawm no, chav tsev ntawm kev ntsuas rau coefficient ntawm resistivity ntawm tus neeg xyuas pib hauv SI yog xam - qhov no yog Ohmm.
Nyob rau hauv cov qauv kev tiv thaiv, p yog cov coefficient tsis kam txiav txim siab los ntawm cov khoom siv tshuaj lom neeg ntawm cov khoom uas tus neeg xyuas pib ua.
Yuav xav txog qhov sib txawv ntawm Ohm txoj cai, peb yuav tsum xav txog ob peb lub tswv yim ntxiv.
tam sim no ceev
Raws li koj paub, hluav taws xob tam sim no yog ib qho kev txav mus los ntawm cov khoom siv hluav taws xob. Piv txwv li, hauv cov hlau, cov khoom thauj tam sim no yog cov khoom siv hluav taws xob, thiab ua cov pa roj, ions.
Tau qhov teeb meem tsis tseem ceeb thaum txhua tus neeg nqa khoom tam sim nohomogeneous - hlau conductor. Cia peb lub siab ib leeg tawm ib qhov ntim me me infinitely hauv tus neeg xyuas pib thiab qhia los ntawm koj qhov nruab nrab (drift, xaj) tshaj tawm ntawm cov hluav taws xob hauv qhov muab ntim. Ntxiv mus, cia n qhia qhov concentration ntawm cov cab kuj tam sim no rau ib chav tsev ntim.
Tam sim no cia peb kos ib thaj tsam infinitesimal dS perpendicular rau vector u thiab tsim raws lub nrawm ib lub tog raj kheej infinitesimal nrog rau qhov siab udt, qhov twg dt qhia lub sijhawm uas tag nrho cov neeg nqa khoom nrawm tam sim no muaj nyob rau hauv qhov kev txiav txim siab yuav dhau mus. dhau ntawm thaj chaw dS.
Nyob rau hauv rooj plaub no, tus nqi sib npaug rau q=neudSdt yuav raug xa los ntawm electrons los ntawm cheeb tsam, qhov twg e yog tus nqi hluav taws xob. Yog li, qhov hluav taws xob tam sim no ceev yog vector j=neu, denoting tus nqi ntawm cov nqi xa mus rau ib lub sij hawm los ntawm ib cheeb tsam.
Ib qho txiaj ntsig ntawm Ohm Txoj Cai Sib txawv txhais yog tias koj tuaj yeem tau txais los ntawm ntau yam tsis suav qhov kev tawm tsam.
nqi hluav taws xob. Lub zog hluav taws xob
Teb lub zog nrog rau cov nqi hluav taws xob yog qhov tseem ceeb hauv kev xav ntawm hluav taws xob. Nyob rau tib lub sijhawm, muaj tswv yim ntau ntawm lawv tuaj yeem tau txais los ntawm kev sim yooj yim muaj rau cov menyuam kawm ntawv.
Rau qhov yooj yim, peb yuav xav txog qhov chaw electrostatic. Qhov no yog qhov chaw hluav taws xob uas tsis hloov nrog lub sijhawm. Xws li daim teb tuaj yeem tsim los ntawm cov nqi hluav taws xob nyob ruaj khov.
Tsis tas li ntawd, yuav tsum tau them nqi kuaj rau peb lub hom phiaj. Hauv nws lub peev xwm peb yuav siv lub cev them nyiaj - me me uas nws tsis muaj peev xwm ua rauib qho kev cuam tshuam (kev faib tawm ntawm cov nqi) hauv cov khoom nyob ib puag ncig.
Cia peb xav txog ob qhov kev xeem nqi coj mus kuaj, ua tiav ntawm ib qho chaw hauv qhov chaw, uas yog nyob rau hauv qhov cuam tshuam ntawm thaj chaw electrostatic. Nws hloov tawm hais tias cov nqi yuav raug rau lub sij hawm-invariant cawv ntawm nws feem. Cia F1 thiab F2 ua tub rog tawm tsam.
Raws li kev nthuav dav ntawm kev sim cov ntaub ntawv, pom tau tias cov rog F1 thiab F2 raug coj los ntawm ib qho lossis nyob rau hauv opposite lus qhia, thiab lawv tus piv F1/F2 yog ywj siab ntawm qhov chaw nyob rau hauv qhov chaw uas cov nqi xeem tau muab tso ua ke. Yog li ntawd, qhov ratio F1/F2 yog tus yam ntxwv ntawm tus nqi them lawv tus kheej, thiab tsis nyob ntawm thaj chaw.
Qhov kev tshawb pom ntawm qhov tseeb no ua rau nws muaj peev xwm ua kom pom qhov hluav taws xob ntawm lub cev thiab tom qab ntawd hu ua hluav taws xob. Yog li, los ntawm txhais, nws hloov tawm q1/q2=F1/F 2 , qhov twg q1 thiab q2 - tus nqi them rau ntawm ib qho chaw, thiab F 1 thiab F2 - quab yuam ua txhaum ntawm sab ntawm lub teb.
Los ntawm cov kev xav li no, qhov loj ntawm cov nqi ntawm ntau yam khoom raug sim tsim. Los ntawm kev teeb tsa ib qho ntawm cov nqi ntsuas sib npaug rau ib qho ntawm qhov sib piv, koj tuaj yeem suav tus nqi ntawm lwm tus nqi los ntawm kev ntsuas qhov ratio F1/F2.
Txhua qhov chaw hluav taws xob tuaj yeem ua tus yam ntxwv los ntawm tus nqi paub. Yog li, lub zog ua haujlwm ntawm qhov ntsuas ntsuas ntawm qhov so yog hu ua lub zog hluav taws xob thiab tau hais los ntawm E. Los ntawm lub ntsiab lus ntawm tus nqi, peb tau txais tias lub zog vector muaj cov qauv hauv qab no: E=F / q.
Kev sib txuas ntawm vectors j thiab E. Lwm daim ntawv ntawm Ohm txoj cai
Nyob rau hauv ib homogeneous conductor, cov lus txib ntawm cov khoom them yuav tshwm sim nyob rau hauv cov kev taw qhia ntawm vectors E. Qhov no txhais tau hais tias cov vectors j thiab E yuav co-directed. Raws li kev txiav txim siab tam sim no, peb xaiv qhov ntim me me cylindrical infinitely hauv tus neeg xyuas pib. Tom qab ntawd ib qho tam sim no sib npaug rau jdS yuav dhau los ntawm ntu ntu ntawm lub tog raj kheej, thiab qhov hluav taws xob siv rau lub tog raj kheej yuav sib npaug rau Edl. Cov mis rau qhov resistivity ntawm ib lub tog raj kheej kuj paub.
Tom qab ntawd, sau cov qauv rau lub zog tam sim no hauv ob txoj hauv kev, peb tau txais: j=E / p, qhov twg tus nqi 1 / p yog hu ua hluav taws xob conductivity thiab yog qhov hloov pauv ntawm hluav taws xob tiv thaiv. Nws yog feem ntau denoted σ (sigma) los yog λ (lambda). Chav tsev ntawm conductivity yog Sm / m, qhov Sm yog Siemens. Unit inverse ntawm Ohm.
Yog li, peb tuaj yeem teb cov lus nug saum toj no hais txog Ohm txoj cai rau lub voj voog tsis sib xws. Hauv qhov no, cov neeg nqa khoom tam sim no yuav raug cuam tshuam los ntawm lub zog los ntawm electrostatic teb, uas yog tus cwj pwm los ntawm kev siv E1, thiab lwm yam quab yuam ua rau lawv los ntawm lwm qhov tam sim no, uas tuaj yeem ua tau. xaiv E 2. Tom qab ntawd Ohm Txoj Cai tau siv rauseem inhomogeneous ntawm cov saw yuav zoo li: j=λ(E1 + E2).
Ntau txog Kev Coj Ua thiab Kev Ua Haujlwm
Lub peev xwm ntawm tus neeg xyuas pib los ua cov hluav taws xob tam sim no yog tus cwj pwm los ntawm nws qhov kev tiv thaiv, uas tuaj yeem pom los ntawm cov qauv ntawm cov resistivity, los yog conductivity, xam raws li qhov sib txuam ntawm conductivity. Tus nqi ntawm cov kev txwv no yog txiav txim siab los ntawm cov khoom siv tshuaj lom neeg ntawm cov khoom siv hluav taws xob thiab los ntawm cov xwm txheej sab nraud. Tshwj xeeb, qhov kub thiab txias.
Rau cov hlau feem ntau, qhov kev tiv thaiv ntawm qhov kub ib txwm yog proportional rau nws, uas yog, p ~ T. Txawm li cas los xij, kev sib txawv yog pom ntawm qhov kub thiab txias. Rau ib tug loj tus naj npawb ntawm cov hlau thiab alloys ntawm qhov kub thiab txias ze rau 0 ° K, qhov kev ua hauj lwm xam pom tias pes tsawg tus nqi. Qhov tshwm sim no hu ua superconductivity. Piv txwv li, mercury, tin, lead, txhuas, thiab lwm yam muaj cov khoom no, Txhua cov hlau muaj nws tus kheej qhov kub thiab txias Tk, qhov tshwm sim ntawm superconductivity tau pom.
Tseem nco ntsoov tias lub ntsiab lus ntawm lub tog raj kheej tiv thaiv tuaj yeem ua rau cov xov hlau ua los ntawm cov khoom qub. Nyob rau hauv cov ntaub ntawv no, tus ntoo khaub lig-sectional cheeb tsam los ntawm lub resistivity formula yuav sib npaug zos rau tus ntoo khaub lig seem ntawm cov hlau, thiab l - nws ntev.
