Cov hluav taws xob conductivity ntawm dielectrics yog ib qho tseem ceeb ntawm lub cev. Cov ntaub ntawv hais txog nws tso cai rau koj txheeb xyuas thaj chaw ntawm kev siv cov ntaub ntawv.
Cov ntsiab lus
Raws li cov khoom siv hluav taws xob tam sim no, cov tshuaj tau muab faib ua pawg:
- dielectrics;
- semiconductors;
- conductors.
Metals yog cov conductors zoo heev tam sim no - lawv cov hluav taws xob conductivity ncav cuag 106-108 (Ohm m)-1.
Thiab cov ntaub ntawv dielectric tsis muaj peev xwm ua hluav taws xob, yog li lawv siv los ua cov khoom thaiv. Lawv tsis muaj cov cab kuj dawb, sib txawv hauv cov qauv dipole ntawm cov molecules.
Semiconductors yog cov khoom siv nrog cov txiaj ntsig nruab nrab.
Kev faib tawm
Tag nrho cov khoom siv dielectric muab faib ua cov polar thiab tsis-polar. Nyob rau hauv polar insulators, qhov chaw ntawm cov nqi zoo thiab tsis zoo yog tawm ntawm qhov chaw. Cov molecules ntawm cov tshuaj no zoo ib yam nyob rau hauv lawv cov hluav taws xob tsis mus rau ib tug nruj dipole, uas muaj nws tus kheej dipole lub sij hawm. Dej tuaj yeem siv los ua polar dielectrics.ammonia, hydrogen chloride.
Tsis yog-polar dielectrics yog qhov txawv ntawm qhov sib txawv ntawm cov chaw ntawm cov nqi zoo thiab tsis zoo. Lawv zoo sib xws hauv cov yam ntxwv hluav taws xob rau ib qho elastic dipole. Piv txwv ntawm cov insulators yog hydrogen, oxygen, carbon tetrachloride.
YElectrical conductivity
Cov hluav taws xob conductivity ntawm dielectrics tau piav qhia los ntawm qhov muaj tsawg tsawg ntawm cov hluav taws xob dawb hauv lawv cov molecules. Nrog rau kev hloov pauv ntawm cov nqi hauv cov khoom nyob rau hauv ib lub sij hawm ntawm lub sij hawm, ib tug maj mam tsim ib tug equilibrium txoj hauj lwm yog pom, uas yog vim li cas rau cov tsos ntawm ib tug tam sim no. Cov hluav taws xob conductivity ntawm dielectrics muaj nyob rau lub sijhawm ntawm kev hloov tawm thiab ntawm qhov voltage. Cov qauv kev ntsuas ntawm cov insulators muaj qhov siab tshaj plaws ntawm tus nqi pub dawb, yog li ntawd, qhov tsis tseem ceeb los ntawm cov dej tam sim no tshwm sim hauv lawv.
Cov hluav taws xob conductivity ntawm dielectrics nyob rau hauv cov ntaub ntawv ntawm ib tug tas li voltage tus nqi yog xam los ntawm tam sim no. Cov txheej txheem no suav nrog kev tso tawm thiab nruab nrab ntawm cov nqi uas twb muaj lawm ntawm cov electrodes. Nyob rau hauv cov ntaub ntawv ntawm alternating voltage, tus nqi ntawm active conductivity yog cuam tshuam tsis tau tsuas yog los ntawm tam sim no, tab sis kuj los ntawm lub active Cheebtsam ntawm lub polarization tam sim no.
Cov khoom hluav taws xob ntawm dielectrics nyob ntawm qhov ceev tam sim no, qhov tsis kam ntawm cov khoom.
Solid Dielectrics
Cov hluav taws xob conductivity ntawm cov khoom siv hluav taws xob tau muab faib ua ntau thiab saum npoo. Txhawm rau sib piv cov kev ntsuas no rau cov khoom sib txawv, cov txiaj ntsig ntawm qhov ntim tshwj xeeb thiab qhov chaw tshwj xeeb yog siv.resistance.
Tag nrho cov conductivity yog qhov suav ntawm ob qhov tseem ceeb, nws tus nqi nyob ntawm cov av noo ntawm ib puag ncig thiab qhov kub thiab txias. Nyob rau hauv cov ntaub ntawv ntawm kev ua hauj lwm tas mus li nyob rau hauv voltage, muaj ib tug txo nyob rau hauv lub tam sim no dhau los ntawm cov kua thiab khoom insulators.
Thiab thaum muaj qhov nce ntawm tam sim no tom qab qee lub sijhawm, peb tuaj yeem tham txog qhov tseeb tias cov txheej txheem hloov tsis tau yuav tshwm sim hauv cov khoom, ua rau kev puas tsuaj (kev tawg ntawm dielectric).
Txoj kev ntawm lub xeev gaseous
Gaseous dielectrics muaj qhov tsis zoo ntawm hluav taws xob conductivity yog tias lub zog ua haujlwm siv rau qhov tsawg kawg nkaus. Qhov tshwm sim ntawm qhov tam sim no hauv cov khoom siv roj ntsha tuaj yeem ua tau tsuas yog nyob rau hauv cov xwm txheej thaum lawv muaj cov hluav taws xob dawb lossis ions them.
Gaseous dielectrics yog cov khoom siv hluav taws xob zoo, yog li lawv tau siv hauv cov khoom siv hluav taws xob niaj hnub hauv cov ntim loj. Ionization hauv cov tshuaj no yog tshwm sim los ntawm lwm yam.
Vim tias muaj kev sib tsoo ntawm cov roj ions, nrog rau kev raug thermal, ultraviolet lossis X-ray raug, cov txheej txheem ntawm kev tsim ntawm nruab nrab molecules (recombination) kuj tau pom. Ua tsaug rau cov txheej txheem no, qhov nce ntawm cov ions hauv cov pa roj yog txwv, qee qhov concentration ntawm cov khoom siv hluav taws xob tau tsim nyob rau lub sijhawm luv luv tom qab raug rau qhov chaw ionization sab nraud.
Nyob rau hauv cov txheej txheem ntawm kev nce qhov voltage thov rau cov roj, qhov kev txav ntawm ions mus rau cov electrodes nce. Lawv tsis yogmuaj sij hawm rau recombine, yog li lawv tawm ntawm cov electrodes. Nrog rau qhov nce ntxiv hauv qhov hluav taws xob, qhov tam sim no tsis nce, nws yog hu ua saturation tam sim no.
Xav txog cov tsis-polar dielectrics, peb nco ntsoov tias huab cua yog ib qho zoo meej insulator.
Ua kua dielectrics
Cov hluav taws xob conductivity ntawm cov kua dielectrics tau piav qhia los ntawm qhov peculiarities ntawm cov qauv ntawm cov kua molecules. Nonpolar cov kuab tshuaj muaj dissociated impurities, nrog rau cov dej noo. Nyob rau hauv polar molecules, qhov conductivity ntawm cov hluav taws xob tam sim no kuj piav qhia los ntawm cov txheej txheem ntawm disintegration rau hauv ions ntawm cov kua nws tus kheej.
Nyob rau hauv lub xeev ntawm kev sib sau ua ke, qhov tam sim no kuj tshwm sim los ntawm kev txav ntawm cov khoom sib txuas. Vim tsis muaj peev xwm tshem tawm cov impurities los ntawm cov dielectric, muaj teeb meem tshwm sim hauv kev tau txais cov kua dej uas tsis tshua muaj tam sim no.
Txhua hom kev rwb thaiv tsev koom nrog kev tshawb nrhiav cov kev xaiv los txo qhov tshwj xeeb conductivity ntawm dielectrics. Piv txwv li, impurities raug tshem tawm, qhov ntsuas kub tau hloov kho. Kev nce hauv qhov kub thiab txias ua rau txo qis hauv viscosity, nce kev txav ntawm ions, thiab nce qib ntawm thermal dissociation. Cov yam ntxwv no cuam tshuam rau cov khoom siv hluav taws xob dielectric.
Electrical conductivity ntawm solids
Nws tau piav qhia los ntawm kev txav ntawm tsis yog cov ions ntawm lub insulator nws tus kheej xwb, tab sis kuj them cov khoom ntawm impurities muaj nyob rau hauv cov khoom siv. Raws li nws dhau los ntawm cov khoom insulator, ib feem tshem tawm ntawm impurities tshwm sim, uas maj mamcuam tshuam qhov conduction. Muab rau hauv tus account cov yam ntxwv ntawm cov siv lead ua lattice, qhov txav ntawm cov khoom siv hluav taws xob yog vim qhov hloov pauv hauv thermal motion.
Ntawm qhov kub thiab txias, qhov zoo thiab tsis zoo impurity ions txav mus. Xws li hom kev rho tawm yog ib yam rau cov khoom uas muaj cov qauv molecular thiab atomic crystal.
Rau anisotropic crystals, tus nqi ntawm cov conductivity tshwj xeeb txawv nyob ntawm nws cov axes. Piv txwv li, nyob rau hauv quartz nyob rau hauv cov kev taw qhia parallel mus rau lub ntsiab axis, nws tshaj lub perpendicular txoj hauj lwm los ntawm 1000 zaug.
Nyob rau hauv cov khoom ntxeem tau dielectrics, qhov uas muaj suab tsis muaj zog, ib tug me ntsis nce nyob rau hauv hluav taws xob kuj ua rau ib tug nce nyob rau hauv lawv cov hluav taws xob kuj. Cov khoom uas muaj dej-soluble impurities qhia qhov txo qis hauv ntim tsis kam vim qhov hloov pauv ntawm cov av noo.
Polarization ntawm dielectrics
qhov tshwm sim no cuam tshuam nrog kev hloov pauv ntawm txoj haujlwm ntawm cov khoom ntawm cov insulator hauv qhov chaw, uas ua rau kom tau txais qee qhov hluav taws xob (induced) lub sijhawm los ntawm txhua lub ntim macroscopic ntawm dielectric.
Muaj polarization uas tshwm sim nyob rau hauv kev cuam tshuam ntawm sab nraud. Lawv kuj paub qhov txawv ntawm qhov hloov pauv ntawm polarization uas tshwm sim txawm tias tsis muaj qhov chaw sab nraud.
Tus txheeb ze permittivity yog tus yam ntxwv los ntawm:
- capacitance ntawm lub capacitor nrog no dielectric;
- nws qhov loj hauv lub tshuab nqus tsev.
txheej txheem no yog nrog los ntawm cov tsos ntawmqhov saum npoo ntawm dielectric ntawm cov nqi khi, uas txo qhov nro hauv cov khoom.
Thaum qhov tsis ua tiav ntawm qhov chaw sab nraud, qhov sib cais ntawm lub dielectric ntim tsis muaj lub sijhawm hluav taws xob, vim tias cov lej ntawm tag nrho cov nqi yog xoom thiab muaj qhov sib txawv ntawm qhov tsis zoo thiab qhov zoo hauv chaw.
xaiv polarization
Thaum lub sijhawm electron polarization, kev hloov pauv tshwm sim nyob rau hauv kev cuam tshuam ntawm sab nraud ntawm lub plhaub hluav taws xob ntawm lub atom. Nyob rau hauv lub ionic variant, kev hloov ntawm lub lattice qhov chaw yog pom. Dipole polarization yog tus cwj pwm los ntawm kev poob los kov yeej kev sib txhuam sab hauv thiab kev sib txuas ua ke. Cov qauv qauv ntawm polarization yog suav tias yog cov txheej txheem qeeb tshaj plaws, nws yog tus cwj pwm los ntawm kev taw qhia ntawm inhomogeneous macroscopic impurities.
Zoo kawg
Cov khoom siv hluav taws xob hluav taws xob yog cov khoom siv uas tso cai rau koj kom tau txais kev rwb thaiv tsev zoo ntawm qee yam khoom siv hluav taws xob hauv qab qee qhov hluav taws xob muaj peev xwm. Piv nrog rau cov conductors tam sim no, ntau cov insulators muaj qhov hluav taws xob ntau dua. Lawv muaj peev xwm tsim cov hluav taws xob muaj zog thiab muaj zog ntxiv. Nws yog cov cuab yeej ntawm insulators uas yog siv nyob rau hauv niaj hnub capacitors.
Nyob ntawm cov tshuaj muaj pes tsawg leeg, lawv muab faib ua cov khoom siv ntuj thiab hluavtaws. Cov pab pawg thib ob yog ntau tshaj plaws, yog li ntawd nws yog cov insulators uas siv ntau yam khoom siv hluav taws xob.
Nyob ntawm cov yam ntxwv thev naus laus zis, qauv, muaj pes tsawg leeg, zaj duab xis, ceramic, wax, ntxhia insulators raug cais tawm.
Thaum qhov kev tawg ntawm qhov hluav taws xob mus txog, qhov kev tawg tau pom, ua rau muaj qhov nce ntxiv ntawm qhov hluav taws xob tam sim no. Ntawm cov yam ntxwv ntawm cov xwm txheej zoo li no, ib tus tuaj yeem tso tawm me ntsis ntawm lub zog ntawm kev ntxhov siab thiab kub, tuab.
