Nkag Siab Txog Cov Ntsiab Cai Dub
Yog tias peb sib tov dej kub thiab dej txias rau hauv lub thawv qhib (piv txwv li, lub thoob), cua sov hloov ntawm dej kub mus rau dej txias. Vim tias lub thawv qhib, qee qhov cua sov hloov mus rau huab cua. Lub thawv kuj sov dua. Cov cua sov uas tso tawm los ntawm dej kub tsis yog tsuas yog nqus los ntawm dej txias xwb tab sis kuj los ntawm huab cua thiab lub thawv. Hauv qhov no, lub thoob yog lub kaw lus tsis cais tawm.
Thaum peb sib tov dej kub thiab dej txias hauv lub thermos kaw, cua sov hloov ntawm dej kub mus rau dej txias. Lub thermos yog ib lub kaw lus cais , yog li tsis muaj cua sov hloov mus rau huab cua lossis lub thermos. Lub cua sov tso tawm los ntawm dej kub tsuas yog nqus los ntawm dej txias kom txog thaum cov khoom sib tov mus txog qhov sib npaug ntawm thermal.
Txoj cai ntawm Black hais tias nyob rau hauv ib lub kaw lus kaw, qhov kub uas tso tawm los ntawm ib yam khoom kub siab = qhov kub uas nqus los ntawm ib yam khoom kub qis.
Cov mis yooj yim ntawm dub
Qtawm = Qnqus tau
Kev piav qhia: Qtawm = cua sov uas tso tawm los ntawm ib yam khoom kub siab, Qnqus tau = cua sov uas cov khoom kub qis nqus tau.
Cov lus nug piv txwv ntawm Black lub hauv paus ntsiab lus
1. Ib daim hlau kub uas hnyav 1 kg thiab kub txog 100 oC muab tso rau hauv ib lub thawv uas muaj dej nrog qhov hnyav ntawm 2 kg thiab qhov kub ntawm 20 oC. Qhov kub kawg ntawm cov khoom sib tov yog dab tsi? Qhov kub tshwj xeeb ntawm hlau = 450 J/kg Co, qhov kub tshwj xeeb ntawm dej = 4200 J/kg Co.
Kev Sib Tham:
Nws yog paub :
m hlau = 1 kg, Tbesi = 100 oC, m dej = 2 kg, Thuab cua = 20 oC, c hlau = 450 J/kg Co, c dej = 4200 J/kg Co.
Nug :
T sib xyaw?
Jawb :
Hlau muaj qhov kub siab dua dej yog li hlau tso tawm cua sov, dej nqus tau cua sov.
(m)(c)(delta T) = (m)(c)(delta T)
(1)(450)(100-T) = (2)(4200)(T-20)
(450)(100-T) = (8400)(T-20)
45000 – 450T = 8400 T – 168000
45000 + 168000 = 8400 T + 450 T
213000 = 8850 T
T = 213000: 8850
TXL = 24 oC
Suhu Qhov kub kawg ntawm kev sib tov ntawm cov hlau kub thiab dej txias thaum ob qho tib si nyob rau hauv thermal equilibrium yog 24 oC.
2. 2015/2016 SMA/MA Physics Kev Xeem Hauv Tebchaws Cov Lus Nug No. 20
75 grams dej ntawm qhov kub ntawm 0 o C yog sib xyaw nrog 50 grams dej kom qhov kub ntawm qhov sib tov yog 40 o C, yog li qhov kub pib ntawm 50 grams dej yog ...
A. 125 o C
B. 120 o C
C. 110 o C
D. 100 o C
E. 80 o C
Kev Sib Tham
Nws paub tias:
Qhov hnyav ntawm dej 1 (m1 ) = 75 grams
Qhov kub pib ntawm dej 1 (T1 ) = 0 o C
Qhov hnyav ntawm dej 2 (m2 ) = 50 grams
Qhov kub kawg ntawm qhov sib tov (T) = 40 o C
Cov units ntawm pawg yog tib yam yog li ntawd tsis tas yuav hloov pauv.
Xav tau: Qhov kub pib ntawm dej 2 (T 2 )
Lus teb:
Txoj cai ntawm Black hais tias nyob rau hauv ib lub kaw lus kaw, qhov kub uas tso tawm los ntawm ib yam khoom kub siab yog sib npaug rau qhov kub uas nqus los ntawm ib yam khoom kub qis.
Q raug tso tawm = Q raug nqus
m 1 c ( Δ T 1 ) = m 2 c ( Δ T 2 )
Qhov kub tshwj xeeb ntawm dej yog tib yam yog li c raug tshem tawm ntawm qhov sib npaug.
m1 ( Δ T1 ) = m2 ( Δ T2 )
(75)(40 – 0) = (50)(T 2 – 40)
(75)(40) = (50)(T 2 – 40)
3000 = 50 T 2 – 2000
3000 + 2000 = 50 T 2
5000 = 50 T 2
T2 = 100
Cov lus teb yog D.
3. 2015/2016 SMA/MA Physics Kev Xeem Hauv Tebchaws Cov Lus Nug Naj Npawb 20
Ib tug hlau 200 gram raug cua sov rau 120 o C ces muab tso rau hauv 100 grams dej ntawm qhov kub ntawm 30 o C. Tom qab sib npaug, qhov kub ntawm qhov sib tov ua 60 o C. Yog tias qhov cua sov tshwj xeeb ntawm dej yog 4200 J.kg -1 o C -1 , ces qhov cua sov tshwj xeeb ntawm cov hlau yog ...
A. 10,5 J.kg -1o C -1
B. 105 J.kg -1o C -1
C. 150 J.kg -1o C -1
D. 1050 J.kg -1o C -1
E. 1500 J.kg -1o C -1
Kev Sib Tham
Kev Hloov Pauv ntawm cov chav loj los ntawm grams mus rau kilograms (International System of Units)
Nws paub tias:
Qhov hnyav ntawm cov hlau (m1 ) = 200 grams = 0,2 kg
Kub ntawm cov hlau (T1 ) = 120 o C
Qhov hnyav ntawm dej (m2 ) = 100 grams = 0,1 kg
Kub ntawm dej (T2 ) = 30 o C
Qhov kub kawg ntawm qhov sib tov (T) = 60 o C
Qhov kub tshwj xeeb ntawm dej (c2 ) = 4200 J.kg -1 o C -1
Nug: Qhov kub tshwj xeeb ntawm cov hlau (c 1 )
Lus teb:
Q raug tso tawm = Q raug nqus
m1 c1 (ΔT1) = m2 c2 (ΔT2)
(0,2)(c 1 )(120 – 60) = (0,1)(4200)(60 – 30)
(0,2)(c 1 )(60) = (0,1)(4200)(30)
12 c 1 = 12600
c 1 = 12600 / 12
c1 = 1050
Cov lus teb yog D.
4. Cov Lus Nug Txog Kev Xeem SMA/MA Xyoo 2018
Muab 250 ml dej npau (100 o C) nchuav rau hauv lub lauj kaub uas muaj 400 ml dej ntawm qhov kub ntawm 35 o C. Tom qab qhov sib npaug ntawm qhov kub thiab txias tshwm sim, qhov kub ntawm qhov sib tov yog ... (qhov kub tshwj xeeb ntawm dej 1,0 cal.gr -1 . o C -1 )
Kev Sib Tham
Nws paub tias:
Qhov kub ntawm dej kub = 100 o C
Qhov ntim dej kub = 250 ml = 0,25 liter = 0,25 dm 3 = (0,25)(1000 cm 3 ) = 250 cm 3
Qhov kub ntawm dej txias = 35 o C
Qhov ntim dej txias = 400 ml = 0,4 liter = 0,4 dm 3 = (0,4)(1000 cm 3 ) = 400 cm 3
Qhov kub tshwj xeeb ntawm dej = 1,0 cal.gr -1 C -1
Qhov Ceev ntawm dej = 1 gr/ cm3
Nug: Qhov kub ntawm kev sib tov
Lus teb:
Xam qhov hnyav ntawm dej kub thiab dej txias siv cov qauv ntom ntom:
m = ρ V
m = pawg, ρ = qhov ceev, V = ntim
Qhov hnyav ntawm dej kub: m = ρ V = ( 1 gr/cm3 ) (250 cm3 ) = 250 grams
Qhov hnyav ntawm dej txias: m = ρ V = ( 1 gr/cm3 ) (400 cm3 ) = 400 grams
Xam qhov kub ntawm qhov sib tov siv Black tus qauv tseem ceeb:
Dej txias nqus cua sov = dej kub tso tawm cua sov
mc Δ T = mc Δ T
Qhov kub tshwj xeeb yog tib yam yog li nws raug tshem tawm ntawm qhov sib npaug.
m Δ T = m Δ T
(400)(T-35) = (250)(100-T)
400T – 14000 = 25000 – 250T
400T + 250T = 25000 + 14000
650T = 39000
T = 39000 / 650
T = 60 oC
