1. Incazelo yesimiso sabamnyama
Uma sixuba amanzi ashisayo nabandayo esitsheni esivulekile (isibonelo ibhakede), ukushisa kuyadlula kusuka emanzini ashisayo kuya emanzini abandayo. Ngenxa yokuthi isitsha sivulekile, khona-ke ukushisa okuthile kuyangena emoyeni. Isitsha siyafudumala futhi. Ukushisa okukhishwa ngamanzi ashisayo akugcini nje ngokumuncwa ngamanzi abandayo, kodwa futhi kuyamuncwa umoya nezitsha. Kulokhu, ibhakede liyisistimu engahlukanisiwe. Uma sixuba amanzi ashisayo nabandayo ku-thermos evaliwe, ukushisa kuyadlula kusuka emanzini ashisayo kuya emanzini abandayo. Ama-thermos ayizinhlelo ezihlukanisiwe, ngakho akukho ukushisa okuya emoyeni noma ku-thermos. Amanzi abandayo amunca kuphela ukushisa okukhishwa ngamanzi ashisayo kuze kube yilapho ingxube yamanzi ashisayo namanzi abandayo ifinyelela ekulinganisweni kokushisa.
Isimiso Esimnyama sithi ohlelweni oluvaliwe oluhlukanisiwe, ukushisa okukhishwa yinto enokushisa okuphezulu = ukushisa okumuncwa yinto enokushisa okuphansi.
2. Ifomula yesimiso esimnyama
Ukukhululwa kwe -Q = ukumuncwa kwe -Q
Ukukhululwa kwe-Q = ukushisa okukhishwa yizinto ezishisa kakhulu, ukumuncwa kwe-Q = ukushisa okumuncwa yizinto ezishisa kakhulu.
3. Izibonelo zemibuzo nezingxoxo
Isibonelo senkinga 1.
Insimbi eshisayo enesisindo esingu-1 kg kanye nokushisa okungu-100 o C ifakwa esitsheni esiqukethe ama-2 kg amanzi kanye nokushisa okungu-20 o C. Lingakanani izinga lokushisa lengxube yokugcina? Ukushisa okuqondile kwensimbi = 450 J/kg Co , ukushisa okuqondile kwamanzi = 4200 J/ kg Co.
Kwaziwa:
Isisindo sensimbi (m) = 1 kg
Izinga lokushisa lensimbi (T) = 100 o C
Isisindo samanzi (m) = 2 kg
Izinga lokushisa lamanzi (T) = 20 o C
Ukushisa okukhethekile kwensimbi (c) = 450 J/kg C o
Ukushisa okuqondile kwamanzi (c) = 4200 J/kg C o
Ufunwa: T?
Isixazululo:
Insimbi inokushisa okuphezulu kunamanzi ngakho insimbi ikhipha ukushisa, amanzi amunca ukushisa.
Ukukhululwa kwe -Q = ukumuncwa kwe -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
Izinga lokushisa lokugcina lenhlanganisela yensimbi eshisayo namanzi abandayo uma kokubili kusesilinganisweni sokushisa lingu-24 o C.
Isibonelo senkinga 2.
Isisindo seqhwa esingu-0.2 kg sixutshwe netiye elifudumele elinesisindo esingu-0.2 kg. Izinga lokushisa leqhwa = -10 o C, izinga lokushisa letiye elifudumele = 40 o C. Ukushisa okuqondile kweqhwa = 2100 J/kg Co , ukushisa okuqondile kwamanzi = 4200 J/kg Co , ukushisa kokuhlanganiswa kwamanzi = 334000 J/kg. Iqhwa netiye kuxutshwa ohlelweni oluhlukanisiwe, oluvaliwe.
Kwaziwa:
Isisindo seqhwa (m) = 0.2 kg
Isisindo setiye (m) = 0.2 kg
Ukushisa kwamanzi okuqondile (c) = 4180 J/kg C o
Ukushisa okuqondile kweqhwa (c) = 2100 J/kg C o
Ukushisa kokuhlanganiswa kwamanzi (L F ) = 334 x 10 3 J/kg
Izinga lokushisa leqhwa ( iqhwa le-T ) = -10 o C
Izinga lokushisa letiye ( itiye le-T ) = 40 o C
Okufunwayo: Ingxube ye-T
Isixazululo:
Isinyathelo sokuqala, linganisa isimo sokugcina
Ukushisa okumele kukhishwe ngamanzi ukuze kuncishiswe izinga lokushisa elingu-0.2 kg wetiye elifudumele, kusukela ku-40 oC kuya ku-0 oC
Ukukhishwa kwe-Q = mc ∆T
Ukukhululwa kwe-Q = (0.2 kg) (4180 J/Kg Co ) (40 o C – 0 o C)
Ukukhululwa kwe-Q = (0.2 kg) (4180 J/Kg Co ) (40 o C)
Ukukhishwa kwe-Q = ama-Joule angu-33,440
Ukukhishwa kwe-Q = 33.44 kJ
Ukushisa kumuncwa yiqhwa elingu-0.2 kg ukuze kwandiswe izinga lokushisa kusuka ku--10 o C kuya ku-0 o C
I-Q emuncwe = mc ∆T
I-Q emuncwe = (0.2 kg) (2100 J/Kg Co ) (0 o C – (-10 o C))
I-Q emuncwe = (0.2 kg) (2100 J/Kg Co ) (10 o C)
I-Q emuncwe = ama-Joule angu-4,200
I-Q emuncwe = 4.2 kJ
Ukushisa kuncibilikiswa ukuze kuncibilikiswe u-0.2 kg weqhwa (ukushisa kuyadingeka ukuze kuncibilikiswe lonke iqhwa emanzini)
Ukuhlanganiswa kwe-Q = m L F
Ukuhlanganiswa kwe-Q = (0.2 kg) (334 x 10 3 J/kg)
Ukuhlanganiswa kwe-Q = 66.8 x 10 3 Joule
Ukuhlanganiswa kwe-Q = 66.8 kJ
Ngokusekelwe ekubalweni okungenhla, imiphumela:
Ukukhishwa kwe-Q = 33.44 kJ
Ukumunca kwe-Q = 4.2 kJ
Ukuhlanganiswa kwe-Q = 66.8 kJ
Uma itiye likhipha ukushisa okufika ku-33.44 kJ, izinga lokushisa letiye liyashintsha kusuka ku-40 o C kuya ku-0 o C. Ukushisa okuthile okukhishwe (cishe ku-4.2 kJ) kusetshenziselwa ukuphakamisa izinga lokushisa leqhwa kusuka ku--10 o C kuya ku-0 o C. 33.44 kJ – 4.2 kJ = 29.24 kJ. Ukushisa okusele = 29.24 kJ. Ukuze kuncibilikiswe lonke iqhwa emanzini kudinga ukushisa okungu-66.8 kJ. Ukushisa okusele kungu-29.24 kJ kuphela.
Ekuphetheni, ukushisa okukhishwa yitiye elifudumele kusetshenziselwa kuphela ukuphakamisa izinga lokushisa leqhwa kusuka ku--10 o C kuya ku-0 o C bese kuncibilikiswa iqhwa elithile. Elinye iqhwa lincibilike laba ngamanzi; amanye alincibilikanga. Ngesikhathi senqubo yokushintsha okuqinile kube uketshezi, izinga lokushisa alishintshi. Ngakho-ke, izinga lokushisa lengxube yokugcina = 0 o C.
Isibonelo senkinga 3.
isisindo setiye elishisayo (m) = 0.4 kg,
isisindo seqhwa (m) = 0.2 kg,
izinga lokushisa leqhwa = -10 o C
izinga lokushisa letiye elishisayo = 90 o C.
Uma zombili zixubile, izinga lokushisa lengxube yokugcina lingakanani?
Ukushisa okuqondile kwamanzi (c) = 4180 J/kg Co2 ,
Ukushisa okuqondile kweqhwa (c) = 2100 J/kg Co2 ,
Ukushisa kokuhlanganiswa kwamanzi (L F ) = 334 x 103 J/kg
Isixazululo:
Isinyathelo sokuqala: Linganisela isimo sokugcina
Ukushisa okumele kukhishwe ngamanzi ukuze kuncishiswe izinga lokushisa elingu-0.4 kg wetiye elishisayo, kusukela ku-90 o C kuya ku-0 o C
Ukukhishwa kwe-Q = mc ∆T
Ukukhululwa kwe-Q = (0.4 kg) (4180 J/Kg Co ) (90 o C – 0 o C)
Ukukhululwa kwe-Q = (0.4 kg) (4180 J/Kg Co ) (90 o C)
Ukukhishwa kwe-Q = ama-Joule angu-150,480
Ukukhishwa kwe-Q = 150.48 kJ
Ukushisa kumuncwa yiqhwa elingu-0.2 kg ukuze kwandiswe izinga lokushisa lalo kusuka ku--10 o C kuya ku-0 o C
I-Q emuncwe = mc ∆T
I-Q emuncwe = (0.2 kg) (2100 J/Kg Co ) (0 o C – (-10 o C))
I-Q emuncwe = (0.2 kg) (2100 J/Kg Co ) (10 o C)
I-Q emuncwe = ama-Joule angu-4,200
I-Q emuncwe = 4.2 kJ
Ukushisa kwakudingeka ukuze kuncibilikiswe iqhwa elingu-0.2 kg (ukushisa kwakudingeka ukuze kuguqulwe lonke iqhwa libe amanzi)
Ukuhlanganiswa kwe-Q = m L F
Ukuhlanganiswa kwe-Q = (0.2 kg) (334 x 10 3 J/Kg)
Ukuhlanganiswa kwe-Q = 66.8 x 10 3 Joule
Ukuhlanganiswa kwe-Q = 66.8 kJ
Ngokusekelwe ekubalweni okungenhla, imiphumela:
Ukukhishwa kwe-Q = 150.48 kJ
I-Q emuncwe = 4.2 kJ
Ukuhlanganiswa kwe-Q = 66.8 kJ
Lapho itiye elishisayo likhipha ukushisa okungu-150.48 kJ, izinga lokushisa letiye elishisayo lashintsha kusuka ku-90 o C kuya ku-0 o C. Ukushisa okuthile okukhishwe (cishe ku-4.2 kJ) kwasetshenziswa ukuphakamisa izinga lokushisa leqhwa kusuka ku--10 o C kuya ku-0 o C.
150.48 kJ – 4.2 kJ = 146.28 kJ. Ukushisa okusele = 146.28 kJ.
Ukushisa okudingekayo ukuze kuncibilikiswe lonke iqhwa emanzini kungu-66.8 kJ kuphela. 146.28 kJ – 66.8 kJ = 79.48 kJ. Kwavela ukuthi okungaphezulu kwakungu-79.48 kJ. Itiye elishisayo alikhiphi konke ukushisa kuze kube yilapho izinga lokushisa lehla laya ku-0 o C. Isiphetho: izinga lokushisa lengxube yokugcina kumele libe ngaphezu kuka-0 o C.
Isinyathelo Sesibili: Thola izinga lokushisa lokugcina (T)
Ukushisa okudingekayo ukwandisa izinga lokushisa leqhwa kusuka ku--10 o C kuya ku-0 o C = 4200 Joules
Ukushisa kwadingeka kuncibilikise lonke iqhwa emanzini, okubizwa nangokuthi ukushisa okucashile = ama-Joules angu-66,800
Ukushisa kwakudingeka kwandise izinga lokushisa lamanzi (amanzi avela kuyo yonke i-ice fusion) kusukela ku-0 o C kuya ku-T = (isisindo seqhwa) (ukushisa kwamanzi) (T – 0 o C) = (0.2 kg) (4180 J/kg Co ) (T) = (836 T) J/C o
Ukushisa okukhishwa yitiye elifudumele ukunciphisa izinga lokushisa kusuka ku-90 o C kuya ku-T = (isisindo samanzi ashisayo) (uhlobo lwamanzi ashisayo) (90 o C – T) = (0.4 kg) (4180 J/kg Co ) (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
Izinga lokushisa lokugcina = 31.7 o C
