12-§. Termodinamikada ish tushinchasi

Berilgan: p = 310^5 Pa A = 1800 J V = ?

Yechish: izobarik jarayonda gazning bajargan ishidan foydalanib uning hajmining o’zgarishi V ni topamiz: . Javob: V = 6 l

2. Bosimi 740 mm simob ustuniga teng bo‘l­gan gaz yuzi 100 sm² bo‘lgan porshenni 9 sm ga surdi. Gaz bajargan ishni aniqlang.

Berilgan: p = 740 mm.s.u. S = 100 sm^-2 h = 9 sm A = ?

Yechish: porshenli silindr ostidagi gaz kengayganda uning bosimi o’zgarmas bo’ladi. Gaz hajmining o’zgarishini porshen yuzasi va porshenning siljishi orqali ifodalab gazning bajargan ishini hisoblaymiz: Javob: A = 88,8 J

3. Kislorod gazi 20 K ga izobarik qizdi­ril­ganda, 16,6 kJ ish bajarildi. Kislorod­ning massasini aniqlang.

Berilgan: M = 32 g/mol T = 20 K p = const A = 16,6 kJ m = ?

Yechish:izobarik jarayonda gazning bajargan ishini gaz temperaturasining o’zgarishi orqali ifodalaymiz: . Bu ifodadan foydalanib gazning massasini hisoblaymiz: Javob: m = 3,2 kg

Mavzuga doir mustaqil masalalar yechish

1.Idishda temperaturasi 27C va massasi 2kg bo’lgan kislorod gazi bor.Gaz izobarik kengayib, 60kJ ish bajarish uchun uni qanday haroratgacha qizdirish kerak? ( J: 415 K )

2. Erkin siljiy oladigan porshen ostidagi harorati 17C, hajmi 10l va bosimi 100kPa bo’lgan gaz 80K ga izobarik qizdirildi.Bunda gaz tashqi kuchlar ustidan qanday ish bajaradi? (J: 1kJ)

3. Erkin siljiy oladigan porshen ostidagi harorati 90K ortganda, gaz izobarik kengayib uning hajmi 5l ga ortdi. Agar gazning harorati yana 30K ga ortsa uning hajmi dastlabki hajmiga qaraganda qanchaga ortadi? Bunda gaz tashqi kuchlar ustidan qanday ish bajargan?

4.Miqdori 25 mol bo’lgan gaz 20K ga isitilganda, izobarik kengayib uning hajmi dastlabki hajmiga nisbatan 20% ga ortdi.Gazning dastlabki temperaturasi qanday bo’lgan? Gaz kengayishida bajarilgan ish nimaga teng? ( J: 100K, 4150 J )