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A. L THUYT V O NHIT I. Nhngvn chung:

1. Khi nimnhit:Nhit l mt trong snhngilng c nhhngrtlnn tnh chtvtcht . Tuy nhinvic xc nh chnh xc mtnhitl mtvn khng ngin. as cc ilngvt lu c th xcnhtrctipnh so snh chngvimtilng cng bncht.Nhit l ilngch c tho gin tipda vo sphthuccatnh chtvtliu vo nhit.

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2. Thang onhit:onhittrchtphithitlp thang onhit. Thang nhittuyti

cthitlpda vo tnh chtca kh l tng.

Thang Kelvin (Thomson Kelvin - 1852): Thang onhitnghctuyti, nvnhit l K. Trong thang o ny ngi ta gn cho nhitcaim cnbngba trng thi ncnchoiwmootj gi trsbng 273,15K.

Thang Celsius (Andreas Celsius - 1742): Thang nhit bch phn, nvnhitl 0C v mt Celsiusbngmt Kelvin.

Nhit Celsius xc nh qua nhit Kelvin theobiuthc :T(0C)=T(K)273,15

Thang Fahrenheit (Fahrenheit1706): nvnhit l F . Trong thang o ny,nhitcaimnc tan l 320F v imnc si l 2120F

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3.Dng c v phng php onhit:

C nhiuloidngconhit, tn gicamloi khc nhau nhngthnggi chung l nhitk

Nhitkl dngc(ngh) onhitbng cch cho chshoc tn hiu l hm sbiti

vinhitBphnnhycmcanhitk lbphnbinnhitnng thnh mt dang nnglng khc

nhn ra c tn hiuvnhit.Nubphnnhycmtip xc vi mi trngcno thgi l nhitkotrctip v ngcli

Khi nimnhitkdng chdngconhitdi 6000C , cn cc nhitkonhit trn6000C gi l hak.

Theo nguyn l onhit, nghnhitc chia lm 5 loi chnh:1/Nhitk dn n

2/Nhitkkiu p k

3/Nhitkintr

4/Cpnhit

5/Hakbcx

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II. Nguyn l onhit:

1. Nhitk dn n:

1.1. Nhitk dn nchtrn:

Nguyn l onhit l da trn dn ndi cachtrn.L = Lt0[1 + (t t0)]

L v Lt0 l di cavt nhit t v t0gi l hs dn ndi cachtrn

Cc loi:

+Nhitkkiua: ccugmmtng kim loi c nh v 1 chica c 2 ln

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+Nhitkkiubn hai kim loi(thng dng lm rowle trong hthngtngng

ngttipim). Hthng dn ndi ca 1 svtliu:

Vtliu Hs dn n di Z(1/)

Nhm Al 0,238.104

0,310.104

ng Cu 0,183.104 0,236.104

Cr - Mn 0,123.104

Thp khng r 0,009.104

H kim Inva(64% Fe & 36% N) 0,00001.104

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1.2. Nhitk dn nchtlng:

Nguyn l: Tngtnh cc loi khc nhngsdngchtlng lm micht(nh Hg, ru)

Cuto: Gm 1 ngthy tinh hocthch anh trong ngchtlngnhthyngn hay chthuc.

uim:ngin, rtin, dsdng, kh chnh xc.

Khuytim: chmtrtngiln, kh cs, dv.

Phn loi:

+ Xt vmt chia thc c 2 loi chnh: hnh chica v loithc chia trong.

+ Xt vmtsdng chia lm cc loi: nhitkkthut, nhitk phng thnghim.

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2. Nhitkintr:

2.1. Nguyn l:Da trn s thay iintr(trkhng) cavtliu theonhit.

Gisnhitkintrc quan hgiaintrv nhit l:Rt = Rt0[1 + (t t0)]

l hsintr; Rt v Rt0 l intrnhit t v t02.2. Nhitkintrkim loi:

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Cutonhitkintr( bphnnhycm)

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3. Nhitknhitin:

Nguyn l:Da vo sxuthinsutnhitinng trong mch khi c chnh lchnhitgia cc uni.

Cuto:Gia cc imtip xc xuthinS k sinh v trong mch c Stng:

EAB = eAB(t) + eBA(t0) + eA(to,t) + eB(to,t)

eAB(t) , eBA(t0) l S k sinh hay inthtiim c nhit t v t0V eA(to,t) v eB(to,t) nh v ngcchiu nhau nn c thb qua, ta c:

EAB = eAB(t) + eBA(t0)

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B. THIT K CM BiNNHIT LM335:

I. Csl thuyt:

1. Giithiu 1 sloicmbinnhit:

2. Cmbinnhit LM335:Cng thc:

R(t)= R0(1 + 3,908.10-3t5,8.10-7t2)

R0: l trkhng caintrti 00C

t :l nhitcaintr(00

C)

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