1. Qeexidda mabda'a Madow
Haddii aan ku qasno biyo kulul iyo kuwo qabow weel furan (tusaale ahaan baaldi), kuleylku wuxuu ka gudbaa biyaha kulul una gudbaa biyo qabow. Maadaama weelku furan yahay, markaas kuleyl qaar ayaa hawada u gudba. Weelku sidoo kale wuu kululaadaa. Kuleylka ay sii daayaan biyaha kulul ma aha oo kaliya inuu nuugo biyaha qabow, laakiin sidoo kale waxaa nuuga jawiga iyo weelasha. Xaaladdan, baaldigu waa nidaam aan go'doon ahayn. Marka aan isku darno biyaha kulul iyo kuwa qabow ee heerkul xiran, kuleylku wuxuu ka gudbaa biyaha kulul una gudbaa biyo qabow. Termuusku waa nidaamyo go'doon ah, sidaa darteed kuleylku ma galo hawada ama heerkulbeeg. Biyaha qabow waxay nuugaan oo keliya kulaylka ay sii daayaan biyaha kulul ilaa isku darka biyaha kulul iyo biyaha qabow uu gaaro dheelitirka kulaylka.
Mabda'a Madow wuxuu sheegayaa in nidaam xiran oo go'doonsan, kulaylka uu sii daayo shay heerkul sare leh = kulayl uu nuugo shay heerkul hooseeya.
2. Qaacidda mabda'a madow
Sii deynta Q = nuugista Q
Sii deynta Q = kulaylka ay sii daayaan walxaha heerkulka sare leh, nuugista Q = kulaylka ay nuugaan walxaha heerkulka hooseeya.
3. Tusaalooyin su'aalo iyo doodo ah
Tusaale ahaan dhibaatada 1aad.
Bir kulul oo cufkeedu yahay 1 kg iyo heerkulkiisu yahay 100 o C ayaa la gelinayaa weel ay ku jiraan 2 kg oo biyo ah iyo heerkulkiisu yahay 20 o C. Waa maxay heerkulka isku darka ugu dambeeya? Kulaylka gaarka ah ee birta = 450 J/kg C o , kulaylka gaarka ah ee biyaha = 4200 J/kg C o.
La yaqaan:
Cufka birta (m) = 1 kg
Heerkulka birta (T) = 100 oC
Cufka biyaha (m) = 2 kg
Heerkulka biyaha (T) = 20 o C
Kulayl gaar ah oo loogu talagalay birta (c) = 450 J/kg C o
Kulayl gaar ah oo loogu talagalay biyaha (c) = 4200 J/kg C o
La rabay: T?
Xalka:
Birtu waxay leedahay heerkul ka sarreeya biyaha sidaa darteed birtu waxay sii deysaa kulaylka, biyuhuna waxay nuugaan kulaylka.
Sii deynta Q = nuugista Q
mc ΔT = mc ΔT
(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 o C
Heerkulka ugu dambeeya ee isku darka birta kulul iyo biyaha qabow marka labaduba ay ku jiraan dheelitirka kulaylka waa 24 o C.
Tusaale ahaan arrinta 2aad.
0.2 kg oo baraf ah oo lagu qasay shaah diirran oo leh cufnaan dhan 0.2 kg. Heerkulka ice = -10 o C, heerkulka shaaha diirran = 40 o C. Kulaylka gaarka ah ee ice = 2100 J/kg C o , kulaylka gaarka ah ee biyaha = 4200 J/kg C o , kulaylka isku-dhafka biyaha = 334000 J/kg. Baraf iyo shaah waxaa lagu qasaa nidaam go'doonsan oo xiran.
La yaqaan:
Cufka barafka (m) = 0.2 kg
Cufka shaaha (m) = 0.2 kg
Kulayl gaar ah oo biyo ah (c) = 4180 J/kg C o
Kulayl gaar ah oo baraf ah (c) = 2100 J/kg C o
Kulaylka isku-dhafka biyaha (L F ) = 334 x 10 3 J/kg
Heerkulka barafka (T baraf ) = -10 o C
Heerkulka shaaha (T shaaha ) = 40 o C
La rabay: Isku darka T
Xalka:
Tallaabada koowaad, qiyaas xaaladda kama dambaysta ah
Kulaylka ay tahay in biyaha lagu sii daayo si loo yareeyo heerkulka 0.2 kg ee shaaha diirran, laga bilaabo 40 oC ilaa 0 oC
Q sii deynta = mc ∆T
Q sii deynta = (0.2 kg) (4180 J/Kg C o ) (40 o C – 0 o C)
Q sii deynta = (0.2 kg) (4180 J/Kg C o ) (40 o C)
Q sii deynta = 33,440 Joule
Q sii deynta = 33.44 kJ
Kuleylka waxaa nuuga 0.2 kg oo baraf ah si loo kordhiyo heerkulka laga bilaabo -10 o C ilaa 0 o C
Q nuugay = mc ∆T
Q oo la nuugo = (0.2 kg) (2100 J/Kg C o ) (0 o C – (-10 o C))
Q oo la nuugo = (0.2 kg) (2100 J/Kg C o ) (10 o C)
Q oo la nuugo = 4,200 Joule
Q oo la nuugo = 4.2 kJ
Kulaylka la nuugo si uu u dhalaaliyo 0.2 kg oo baraf ah (kuleylka loo baahan yahay si barafka oo dhan loogu dhalaaliyo biyo)
Isku-darka Q = m L F
Isku-darka Q = (0.2 kg) (334 x 10 3 J/kg)
Isku-darka Q = 66.8 x 10 3 Joule
Isku-darka Q = 66.8 kJ
Iyadoo lagu saleynayo xisaabinta kor ku xusan, natiijooyinka:
Q sii deynta = 33.44 kJ
Q nuugista = 4.2 kJ
Isku-darka Q = 66.8 kJ
Marka shaaha uu sii daayo kulayl dhan 33.44 kJ, heerkulka shaaha wuxuu ka beddelaa 40 o C ilaa 0 o C. Kulayl la sii daayo (qiyaastii 4.2 kJ) ayaa loo isticmaalaa in lagu kordhiyo heerkulka barafka laga bilaabo -10 o C ilaa 0 o C. 33.44 kJ – 4.2 kJ = 29.24 kJ. Kulaylka soo haray = 29.24 kJ. Si barafka oo dhan loogu dhalaaliyo biyo waxay u baahan tahay kulayl dhan 66.8 kJ. Kulaylka soo haray waa 29.24 kJ oo keliya.
Gunaanadkii, kulaylka uu sii daayo shaaha diirran waxaa loo isticmaalaa oo keliya in heerkulka barafka laga kordhiyo -10 o C ilaa 0 o C oo lagu dhalaaliyo baraf. Qaar ka mid ah barafku wuu dhalaalay oo biyo ayuu isu beddelay; qaarna ma dhalaalin. Inta lagu jiro habka loo beddelayo mid adag oo dareere ah, heerkulku isma beddelo. Sidaa darteed, heerkulka isku darka ugu dambeeya = 0 o C.
Tusaale ahaan dhibaatada 3aad.
cufnaanta shaaha kulul (m) = 0.4 kg,
cufnaanta barafka (m) = 0.2 kg,
heerkulka barafka = -10 o C
heerkulka shaaha kulul = 90 o C.
Haddii labaduba isku dhafan yihiin, waa maxay heerkulka isku darka ugu dambeeya?
Kulaylka gaarka ah ee biyaha (c) = 4180 J/kg C o ,
Kulaylka gaarka ah ee barafka (c) = 2100 J/kg C o ,
Kulaylka isku-dhafka biyaha (L F ) = 334 x 103 J/kg
Xalka:
Tallaabada koowaad: Qiyaas xaaladda kama dambaysta ah
Kulaylka ay tahay in biyaha lagu sii daayo si loo yareeyo heerkulka 0.4 kg oo shaah kulul ah, laga bilaabo 90 o C ilaa 0 o C
Q sii deynta = mc ∆T
Q sii deynta = (0.4 kg) (4180 J/Kg C o ) (90 o C – 0 o C)
Q sii deynta = (0.4 kg) (4180 J/Kg C o ) (90 o C)
Q sii deynta = 150,480 Joule
Q sii deynta = 150.48 kJ
Kulaylka uu nuugo 0.2 kg oo baraf ah si uu u kordhiyo heerkulkiisa laga bilaabo -10 o C ilaa 0 o C
Q nuugay = mc ∆T
Q oo la nuugo = (0.2 kg) (2100 J/Kg C o ) (0 o C – (-10 o C))
Q oo la nuugo = (0.2 kg) (2100 J/Kg C o ) (10 o C)
Q oo la nuugo = 4,200 Joule
Q oo la nuugo = 4.2 kJ
Kulaylku wuxuu u baahnaa inuu dhalaaliyo 0.2 kg oo baraf ah (kuleylka loo baahan yahay si barafka oo dhan loogu beddelo biyo)
Isku-darka Q = m L F
Isku-darka Q = (0.2 kg) (334 x 10 3 J/Kg)
Isku-darka Q = 66.8 x 10 3 Joule
Isku-darka Q = 66.8 kJ
Iyadoo lagu saleynayo xisaabinta kor ku xusan, natiijooyinka:
Q sii deynta = 150.48 kJ
Q oo la nuugo = 4.2 kJ
Isku-darka Q = 66.8 kJ
Markii shaaha kulul uu sii daayay 150.48 kJ oo kuleyl ah, heerkulka shaaha kulul wuxuu ka beddelay 90 o C ilaa 0 o C. Kuleyl la sii daayay (qiyaastii 4.2 kJ) ayaa loo isticmaalay in lagu kordhiyo heerkulka barafka laga bilaabo -10 o C ilaa 0 o C.
150.48 kJ – 4.2 kJ = 146.28 kJ. Kulaylka haray = 146.28 kJ.
Kulaylka loo baahan yahay si barafka oo dhan loogu dhalaaliyo biyaha waa 66.8 kJ oo keliya. 146.28 kJ – 66.8 kJ = 79.48 kJ. Waxaa soo baxday in xad-dhaafka uu ahaa 79.48 kJ. Shaaha kulul ma sii daayo kulaylka oo dhan ilaa heerkulka laga dhimo 0 o C. Gunaanad: heerkulka isku darka ugu dambeeya waa inuu ka weynaadaa 0 o C.
Tallaabada Labaad: Go'aami heerkulka kama dambaysta ah (T)
Kulaylka loo baahan yahay si loo kordhiyo heerkulka barafka laga bilaabo -10 o C ilaa 0 o C = 4200 Joules
Kulaylku wuxuu ahaa inuu barafka oo dhan u dhalaaliyo biyo ama kulayl qarsoon = 66,800 Joules
Kulaylku wuxuu ahaa inuu kordhiyo heerkulka biyaha (biyaha ka yimaada isku-dhafka barafka oo dhan) laga bilaabo 0 o C ilaa T = (cufnaanta barafka) (kuleylka biyaha) (T – 0 o C) = (0.2 kg) (4180 J/kg C o )(T) = (836 T) J/C o
Kulaylka uu sii daayo shaaha diirran si loo yareeyo heerkulka laga bilaabo 90 o C ilaa T = (cufnaanta biyaha kulul) (nooca kulaylka biyaha) (90 o C – T) = (0.4 kg) (4180 J/kg C o ) (90 o C – T) = 1672 J/C o (90 o C – T) = 150,480 J – (1672 T) J/C o
4200 J + 66,800 J + (836 T) J/C o = 150,480 J – (1672 T) J/C o
71,000 J + (836 T) J/C o = 150,480 J – (1672 T) J/C o
(836 T) J/C o + (1672 T) J/C o = 150,480 J – 71,000 J
(2508 T) J/C o = 79,480 J
T = 31.7 o C
Heerkulka kama dambaysta ah = 31.7 o C
