To taub Ohm txoj cai lij choj
Tsis tas li ntawd, kawm cov ntaub ntawv hais txog Ohm txoj cai piv txwv cov lus nug thiab kev sib tham txog Ohm txoj cai cov lus nug.
Yuav luag txhua tus hlau conductors, lub zog hluav taws xob sib npaug rau qhov ceev ntawm hluav taws xob tam sim no, qhov twg qhov piv ntawm lub teb hluav taws xob rau qhov ceev ntawm tam sim no hluav taws xob yog qhov ruaj khov. Kev qhia lej los ntawm cov qauv:
ρ = E / J
Kev piav qhia: E = lub teb hluav taws xob, ρ = resistivity, J = qhov ceev ntawm hluav taws xob tam sim no.
Qhov sib piv tas li ρ yog hu ua qhov tsis kam tshwj xeeb lossis resistivity, tus nqi ntawm nws yog tas li thiab tsis nyob ntawm lub teb hluav taws xob uas tsim cov hluav taws xob tam sim no.
Yog tias lub teb hluav taws xob nce ntxiv, qhov ceev ntawm lub zog hluav taws xob kuj nce ntxiv, qhov sib piv, yog tias lub teb hluav taws xob txo qis, qhov ceev ntawm lub zog hluav taws xob kuj txo qis, yog li qhov sib piv ntawm lub teb hluav taws xob rau qhov ceev ntawm lub zog hluav taws xob yog qhov tas li. Qhov no yog ib daim ntawv qhia txog Ohm txoj cai . Yog li cov kab zauv saum toj no piav qhia txog Ohm txoj cai tsuas yog thaum ρ yog qhov tas li thiab ywj pheej ntawm lub teb hluav taws xob. Ohm txoj cai tsis siv yog tias tus nqi ntawm ρ hloov pauv thaum lub teb hluav taws xob hloov pauv.
Txawm li cas los xij, nws yooj yim dua los ntsuas lub zog hluav taws xob (V) dua li lub teb hluav taws xob (E), thiab nws kuj yooj yim dua los ntsuas lub zog hluav taws xob (I) dua li lub zog hluav taws xob ceev (J). Yog li ntawd, ntxiv rau qhov tau hais tawm hauv cov nqe lus ntawm lub teb hluav taws xob , lub zog hluav taws xob ceev thiab resistivity (ρ), Ohm txoj cai kuj tau hais tawm hauv cov nqe lus ntawm lub zog hluav taws xob , lub zog hluav taws xob thiab lub zog hluav taws xob tsis kam (R).
Ua ntej, xav txog ib lub xov hlau uas muaj qhov ntev (l), thaj tsam hla (A) thiab muaj qhov sib txawv ntawm lub zog hluav taws xob (V) ntawm ob sab ntawm cov xov hlau. Yog tias lub teb hluav taws xob yog homogeneous, aka tib yam thoob plaws, ces kev sib raug zoo ntawm lub teb hluav taws xob thiab qhov sib txawv ntawm lub zog hluav taws xob tau qhia hauv kab zauv V = E s ( kab zauv no tau tham txog hauv cov khoom siv hluav taws xob ). Yog tias qhov ceev ntawm tam sim no yog homogeneous, aka tib yam thoob plaws, ces kev sib raug zoo ntawm qhov ceev ntawm tam sim no thiab tam sim no tau qhia hauv kab zauv I = JA ( kab zauv no tau tham txog hauv cov khoom siv hluav taws xob ).
Yuav kom tau ib qho equation uas qhia txog kev sib raug zoo ntawm lub zog fais fab (V), tam sim no fais fab (I) thiab lub zog tiv thaiv fais fab (R), hloov E thiab J hauv qhov equation tiv thaiv nrog E hauv qhov equation zog fais fab thiab J hauv qhov equation tam sim no fais fab:
Qhov no yog ib qho kev sib npaug uas piav qhia txog kev sib raug zoo ntawm lub zog hluav taws xob (V), tam sim no (I) thiab kev tiv thaiv hluav taws xob (R) hauv tus neeg xyuas hluav taws xob. Raws li qhov kev sib npaug no, nws tuaj yeem hais tias qhov kev tiv thaiv hluav taws xob hauv tus neeg xyuas hluav taws xob yog qhov sib piv ntawm qhov sib txawv ntawm lub zog hluav taws xob rau tam sim no hauv tus neeg xyuas hluav taws xob.
Txoj cai Ohm hais tias qhov sib piv ntawm qhov sib txawv ntawm lub zog hluav taws xob rau tam sim no hluav taws xob yog qhov tsis hloov pauv. Hauv lwm lo lus, qhov kev sib npaug no piav qhia txog txoj cai Ohm tsuas yog thaum lub zog hluav taws xob tsis hloov pauv (R) yog qhov tsis hloov pauv. Txoj cai Ohm tsis siv yog tias lub zog hluav taws xob tsis hloov pauv, piv txwv li, nws hloov pauv.
Hauv kev txiav txim siab ntawm qhov sib npaug saum toj no, qhov hluav taws xob tsis kam (R) ntawm tus neeg xyuas pib kuj muaj feem cuam tshuam nrog qhov tsis kam tshwj xeeb (ρ), qhov ntev ntawm tus neeg xyuas pib (l) thiab thaj tsam hla-sectional (A) ntawm tus neeg xyuas pib. Hauv lej, qhov no tau qhia hauv qhov sib npaug:
Cov kab zauv no tau tham txog ntau ntxiv hauv tsab xov xwm txog kev tiv thaiv hluav taws xob.
Cov Qauv Cai ntawm Ohm
Txoj cai Ohm piav qhia los ntawm ob qho kev sib npaug, uas yog ρ = E/J thiab R = V/I. Yuav tsum nco ntsoov tias ob qho kev sib npaug no yog Ohm txoj cai sib npaug tsuas yog thaum ρ yog qhov tsis hloov pauv thiab R yog qhov tsis hloov pauv. Yog tias ρ thiab R ntawm tus neeg coj hluav taws xob hloov pauv, ob qho kev sib npaug no tsis piav qhia Ohm txoj cai, tab sis ρ = E/J piav qhia txog qhov tsis kam ntawm tus neeg coj hluav taws xob thiab R = V/I piav qhia txog qhov tsis kam hluav taws xob ntawm tus neeg coj hluav taws xob.
Tus qauv ρ = E/J sau tau ua E = ρ J. Thaum ρ tsis hloov pauv ces E yog sib npaug ncaj qha rau J, txhais tau tias yog E nce ces J nce lossis yog E txo qis ces J txo qis.
Ib yam li ntawd, tus qauv R = V/I tuaj yeem sau ua V = I R. Thaum R tsis hloov pauv, V yog ncaj qha rau I, txhais tau tias yog V nce, I nce, lossis yog V txo qis, I txo qis.
Cov ntaub ntawv uas ua raws li Ohm txoj cai hu ua ohmic, thaum cov ntaub ntawv uas tsis ua raws li Ohm txoj cai hu ua nonohmic. Yuav luag txhua tus hlau conductors yog ohmic, thaum ntau lwm yam ntaub ntawv yog nonohmic.
Hauv cov ntaub ntawv uas tsis yog ohmic, qhov hluav taws xob tsis ruaj khov, tab sis nws txawv nyob ntawm qhov tam sim no thiab qhov sib txawv ntawm qhov muaj peev xwm. Qhov no txhais tau tias yog tias qhov tam sim no hloov, qhov tsis kam ntawm cov khoom kuj hloov, thiab ib yam li ntawd, yog tias qhov hluav taws xob hloov, qhov tsis kam ntawm cov khoom kuj hloov. Vim tias qhov hluav taws xob tsis kam hloov, hauv cov ntaub ntawv uas tsis yog ohmic, qhov hluav taws xob (V) tsis sib npaug ncaj qha rau qhov tam sim no (I).
Cov duab V, I thiab R
Hauv cov ntaub ntawv ohmic, qhov piv ntawm V rau I yog qhov tsis hloov pauv, sawv cev los ntawm ib txoj kab ncaj. Piv txwv ntawm cov ntaub ntawv ohmic yog cov hlau conductors. Lub caij no, hauv cov ntaub ntawv nonohmic, qhov piv ntawm V rau I tsis hloov pauv, sawv cev los ntawm ib txoj kab nkhaus. Piv txwv ntawm cov ntaub ntawv nonohmic yog semiconductor diodes thiab transistors.
Txoj cai Ohm tsuas yog siv rau cov khoom siv ohmic xwb thiab tsis yog rau txhua yam khoom siv, yog li nws tsis yog qhov tseeb uas hu nws ua txoj cai zoo li Newton txoj cai lossis lwm txoj cai ntawm physics. Cov kev cai ntawm physics yeej siv rau txhua yam khoom, tsis yog rau qee yam khoom xwb. Txawm li cas los xij, kev siv txoj cai Ohm tau dhau los ua ib qho kev coj ua, yog li nws tseem hu ua txoj cai Ohm, tsuav yog nws nco qab tias txoj cai Ohm tsuas yog siv rau cov khoom ohmic xwb. Dhau li ntawm txoj cai Ohm, lwm qhov piv txwv ntawm kev nkag siab yuam kev yog kev siv txoj cai roj zoo tagnrho lossis txoj cai Hooke.
