Kumvetsetsa Mfundo za Anthu Akuda
Ngati tisakaniza madzi otentha ndi ozizira mu chidebe chotseguka (monga chidebe), kutentha kumasamuka kuchoka pamadzi otentha kupita ku madzi ozizira. Chifukwa chidebecho chili chotseguka, kutentha kwina kumasamuka kupita mumlengalenga. Chidebecho chimafundanso. Kutentha komwe kumatulutsidwa ndi madzi otentha sikumangotengedwa ndi madzi ozizira komanso ndi mpweya ndi chidebecho. Pankhaniyi, chidebecho sichimayikidwa paokha.
Tikasakaniza madzi otentha ndi ozizira mu thermos yotsekedwa, kutentha kumasamutsidwa kuchokera ku madzi otentha kupita ku madzi ozizira. Thermos ndi dongosolo lokhalokha , kotero kutentha sikusamutsidwa kupita ku mpweya kapena thermos. Kutentha komwe kumatulutsidwa ndi madzi otentha kumangotengedwa ndi madzi ozizira mpaka chisakanizocho chifike pamlingo wofanana ndi kutentha.
Mfundo ya Black imati mu dongosolo lotsekedwa lokha, kutentha komwe kumatulutsidwa ndi chinthu chotentha kwambiri = kutentha komwe kumatengedwa ndi chinthu chotentha pang'ono.
Fomula yoyambira ya Black
Qkuzimitsa =Qkuyamwa
Kufotokozera: Qkuzimitsa = kutentha komwe kumatulutsidwa ndi chinthu chotentha kwambiri, Qkuyamwa = kutentha komwe kumatengedwa ndi zinthu zotentha pang'ono.
Mafunso a chitsanzo cha mfundo za Black
1. Chitsulo chotentha chokhala ndi kulemera kwa 1 kg ndi kutentha kwa 100 oC imayikidwa mu chidebe chokhala ndi madzi olemera 2 kg ndi kutentha kwa madigiri 20 oC. Kodi kutentha komaliza kwa chisakanizocho ndi kotani? Kutentha kwapadera kwa chitsulo = 450 J/kg Co, kutentha kwa madzi = 4200 J/kg Co.
Kukambirana:
Ndizodziwika kuti :
m chitsulo = 1 kg, Tkunenepa = 100 oC, m madzi = 2 kg, Tmpweya = 20 oC, c chitsulo = 450 J/kg Co, c madzi = 4200 J/kg Co.
Anafunsa :
Kusakaniza kwa T?
Yankhani :
Chitsulo chimakhala ndi kutentha kwakukulu kuposa madzi kotero chitsulo chimatulutsa kutentha, madzi amayamwa kutentha.
(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
T = 24 oC
Suhu Kutentha komaliza kwa chisakanizo cha chitsulo chotentha ndi madzi ozizira pamene zonse zili mu kutentha ndi madigiri 24. oC.
2. 2015/2016 SMA/MA Fizikisi Funso la Mayeso a Dziko Nambala 20
Magalamu 75 a madzi pa kutentha kwa 0 ° C amasakanizidwa ndi magalamu 50 a madzi kotero kuti kutentha kwa chisakanizocho ndi 40 ° C, kotero kutentha koyambirira kwa magalamu 50 a madzi ndi...
A. 125 o C
B. 120 o C
C. 110 o C
D. 100 o C
E. 80 o C
Zokambirana
Amadziwika kuti:
Unyinji wa madzi 1 (m1 ) = magalamu 75
Kutentha koyambirira kwa madzi 1 (T 1 ) = 0 o C
Unyinji wa madzi 2 (m2 ) = magalamu 50
Kutentha komaliza kwa chisakanizo (T) = 40 o C
Mayunitsi a kulemera ndi ofanana kotero palibe kusinthika komwe kumafunika.
Kufunika: Kutentha koyambirira kwa madzi 2 (T 2 )
Yankho:
Mfundo ya Black imati mu dongosolo lotsekedwa lokhalokha, kutentha komwe kumatulutsidwa ndi chinthu chotentha kwambiri kumakhala kofanana ndi kutentha komwe kumatengedwa ndi chinthu chotentha pang'ono.
Q yatulutsidwa = Q yatengedwa
m 1 c ( Δ T 1 ) = m 2 c ( Δ T 2 )
Kutentha kwa madzi kwenikweni ndi komweko kotero c imachotsedwa mu equation.
m 1 ( Δ T 1 ) = m 2 ( Δ T 2 )
(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
T 2 = 100
Yankho lolondola ndi D.
3. 2015/2016 SMA/MA Fiziki Funso Ladziko Lonse la Mayeso Nambala 20
Chitsulo cha magalamu 200 chimatenthedwa kufika pa 120 o C kenako chimayikidwa mu magalamu 100 a madzi pa kutentha kwa 30 o C. Pambuyo pa kulinganiza, kutentha kwa chisakanizocho kumakhala 60 o C. Ngati kutentha kwa madzi ndi 4200 J.kg -1 o C -1 , ndiye kuti kutentha kwa chitsulocho ndi...
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
Zokambirana
Kusintha kwa mayunitsi a kulemera kuchokera ku magalamu kupita ku ma kilogalamu (International System of Units)
Amadziwika kuti:
Kulemera kwa chitsulo (m 1 ) = magalamu 200 = 0,2 kg
Kutentha kwachitsulo (T 1 ) = 120 o C
Madzi olemera (m2 ) = magalamu 100 = 0,1 kg
Kutentha kwa madzi (T 2 ) = 30 o C
Kutentha komaliza kwa chisakanizo (T) = 60 o C
Kutentha kwa madzi enieni (c 2 ) = 4200 J.kg -1 o C -1
Yafunsidwa: Kutentha kwachitsulo (c 1 )
Yankho:
Q yatulutsidwa = Q yatengedwa
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
c 1 = 1050
Yankho lolondola ndi D.
4. Mafunso a Mayeso a Dziko Lonse a SMA/MA a 2018
Madzi otentha okwana 250 ml (100 o C) amathiridwa mumphika wokhala ndi 400 ml ya madzi pa kutentha kwa 35 o C. Pambuyo pa kutentha kwabwino, kutentha kwa chisakanizocho ndi… (kutentha kwapadera kwa madzi 1,0 cal.gr -1 .o C -1 )
Zokambirana
Ndizodziwika kuti:
Kutentha kwa madzi otentha = 100 o C
Kuchuluka kwa madzi otentha = 250 ml = 0,25 lita = 0,25 dm 3 = (0,25)(1000 cm 3 ) = 250 cm 3
Kutentha kwa madzi ozizira = 35 o C
Kuchuluka kwa madzi ozizira = 400 ml = 0,4 lita = 0,4 dm 3 = (0,4)(1000 cm 3 ) = 400 cm 3
Kutentha kwa madzi enieni = 1,0 cal.gr -1 . o C -1
Kuchuluka kwa madzi = 1 gr/ cm3
Anafunsa: Kutentha kwa chisakanizo
Yankho:
Werengerani unyinji wa madzi otentha ndi ozizira pogwiritsa ntchito njira yowerengera kuchuluka kwa madzi:
m = ρ V
m = kulemera, ρ = kuchuluka, V = voliyumu
Madzi otentha ambiri: m = ρ V = ( 1 gr/cm 3 )(250 cm 3 ) = 250 magalamu
Madzi ozizira ambiri: m = ρ V = ( 1 gr/cm 3 )(400 cm 3 ) = 400 magalamu
Werengerani kutentha kwa chisakanizo pogwiritsa ntchito njira ya Black:
Kutentha komwe kumatengedwa ndi madzi ozizira = kutentha komwe kumatulutsidwa ndi madzi otentha
mc Δ T = mc Δ T
Kutentha kwenikweni ndi komweko kotero kumachotsedwa mu equation.
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 o C
