12-§. Termodinamikada ish tushinchasi

Gaz bajargan ishining geometrik talqini. Gazning bosimi o‘zgarmas bo‘lgan holda bajar­gan ishining geometrik talqinini sodda­gina izohlash mumkin. Buning uchun gaz bosimining hajmi­ga bog‘lanish grafigini chizamiz (16-rasm). O‘z­garmas p₁ bosimga ega bo‘lgan gazning hajmi V₁ dan V₂ ga kengayganda bajarilgan ish abcd to‘g‘ri to‘rtburchakning yuziga son jihat­dan teng, ya’ni:

16-rasm

17-rasm

A Izotermik jarayonda bosim hajmga teskari proporsional ravishda o‘zgaradi (17-rasm). Bu holda gazning bajargan ishi son jihatdan izoterma grafigi ostidagi shtixlangan yuzaga teng bo’ladi.

O’zgaruvchan kuchning bajargan ishini hisoblaganimiz kabi oz’garuvchan bosim ostida gaz hajmining V₁ dan V₂ gacha kengayishda bajargan ishi ham uning bir nechta elementar kengayishlarida bajargan ishlarining yig’indisiga teng bo’lib, 18 -rasmda ko’rsatilgan barcha shakllar yuzasidan iborat. Demak, har qanday jarayonda berilgan gazning kengayishida bajargan ishi bu jarayonni p – V diagrammada tasvirlovchi grafik shakilning yuzasiga son jihatdan teng bo’ladi.

18-rasm

Nazorat uchun savollar

1. Gazning izobarik kengayishida bajargan ishi formulasini keltirib chiqaring va uni izohlang.

2. Gazning izobarik kengayishida bajargan ishini haroratning o’zgarishi orqali ifodalang.
3.Mexanikada bajarilgan ish bilan termodinamikadagi bajarilgan ish orasida farq nimada?
Mavzuga doir masala yechish namunalari

1. Silindrik idishdagi 0,3 MPa bosim ostida turgan gaz izobarik ravishda kengayib, 1800 J ish bajardi. Bunda gazning hajmi qanchaga ortgan.