Termodinamika
191
,63E296C:?2B?DH2?86?88E?22?B6C6BF:B CE9E D:?88:
6:=:: 67:C:6?C:
.?DE
6?2:2?67:C:6?C:?H26?;25:
36B2A256B2;2D CE9EB6C6BF:BD:?88:92BEC5:?2:2?
6C:? 2B?D H2?8 36BCE9E B6C6BF:B D:?88:
L 6:=::67:C:6?C:
7:C:6?C:52B:6C:?D6BC63ED
5:D:?82D2? 6?;25:
6B2A2 56B2;2D CE9E B6C6BF:BD:?88:92BEC5:?2:2?
6C:? 2B?D 6?6B:2 2=B 52B: B6C6BF:B H2?8 36BCE9ED:?88:L52?6=6A2C2??H2A252CE9E
B6?529L-6?DE2?67:C:6?C:6C:?2B?DD6BC63ED 6C:? A6?5:?8:? BE2?82? 6?H6B2A 2=B C636C2B
;E=652=2G2DEC6?:2CE9EBE2?82? 22?5:A6BD292?2?C636C2BLC652?82?CE9E
Tes Kompetensi Subbab
C
2+,--.5,5-4 =:?8E?82?D6A2DA63E2?82?2=B252=29
L
6B2A22952H2=:CDB:H2?85:3EDE92? ,63E296C:?6?H6B2A2=BC636C2B
E=652B:
C63E29B6C6BF:B36BCE9E
52?63E2?8?H2 C636C2B
;E=6A252CE9E
2B:52D2D6BC63ED
D6?DE2?=29 2
67:C:6?C:6C:?52? 3
EC292H2?852A2D5:=2E2? ,63E296C:?2B?D6:=::67:C:6?C:
:2CE9E
B6C6BF:BD:?88:
D6?DE2?=2936C2B?H2CE9E B6C6BF:B D:?88: 282B 67:C:6?C: 6C:? 6?;25:
56?82? 2?882A2? CE9E B6C6BF:B B6?529 D:52 6?82=2:A6BE3292?
D. Hukum II Termodinamika
EE -6B5:?2:2 6?H2D22? D6?D2?8 662=2? 6?6B8: H2:DE 6?6B8:D:5252A2D5:4:AD22?2D2E5:EC?292?6=2:?2?92?H252A2D5:E329
52B: C2DE 36?DE 6?6B8: 6 36?DE 6?6B8: =2:??H2 EE -6B5:?2:2 D:52632D2C:3282:2?2A6BE3292?6?6B8:D6BC63ED36B=2?8CE?82:?92=?H2
56?82?EE-6B5:?2:2H2?86:=::32D2C2?32D2C2?D6BD6?DE
,63E29 6C:? 52A2D 36B86B2 5:C63232? 252?H2 6?6B8: 2=B H2?8 5:36B:2?A2526C:?D6BC63EDC642B2D6BEC6?6BECD6D2A:C632=:?H2D:52
E?8:? 6?6B8: 86B2 EC292 52A2D 636B:2? 2=B C642B2 D6BEC 6?6BEC 252 6?H2D22??H2 D:52 252 C63E29 6C:? AE? H2?8 366B;2
6?H6B2A 6?6B8: 2=B 52? 6?8E329 C6=EBE9?H2 6?;25: EC292
6B:ED:?:92=92=H2?836B2:D2?56?82?EE-6B5:?2:2 H2?8 6BEA22? 6C:AE=2? 52B: A6?822D2?A6?822D2? H2?8
5:=2E2? =69 -6 -, 52? -5353 6?EBED 6=F:? 52? =2?4 D:52 E?8:? 63E2D 6C:? H2?8
366B;2 52=2 CE2DE C:=EC 6?6B:2 2=B 52B: C2DE B6C6BF:B 52? 6?8E329 C6=EBE9 2=B D6BC63ED 6?;25: EC292
6?EBED=2EC:ECD:52E?8:?63E2D6C:?H2?8366B;252=2 C2DEC:=EC6?823:=2=B52B:B6C6BF:BH2?86:=::CE9EB6?529
52? 636B:2??H2 A252 B6C6BF:B H2?8 6:=:: CE9E D:?88: D2?A2 66B=E2? EC292 52B: =E2B
6C:?2B?DH2?8366B;25:2?D2B2B6C6BF:BCE9E 52?B6C6BF:B
H2?8 36BCE9E 6?892C:=2? 67:C:6?C: H2?8 D:?88:
25: 6?EBED 6=F:? 52? =2?4 D:52 E?8:? CE2DE 6C:? 92?H2 6:=:: C63E29 B6C6BF:B 52? D:52 E?8:? C63E29 6C:? 6:=::
67:C:6?C:
:267:C:6?C:
2=BH2?85:C6B2A52B:=:?8E?82??H2 22?5:E329C6=EBE9?H26?;25:EC292.C2926C:?C6242:?:5:C63ED
6C:? ,-,00+;6?:C65E26?H2D22??H2D:522526C:?C6A6BD:
:DE G2=2EAE? 2C:9 66?E9: EE -6B5:?2:2
Tokoh
Nikolaus Otto
Pada 1876, seorang warga negara Jerman, Nikolaus Otto menjadi orang
pertama yang membuat dan menjual mesin 4 tak yang kemudian menjadi
dasar pembuatan kebanyakan mesin. Ia menamakan mesinnya Silent Otto
karena mesin tersebut mampu bekerja tanpa menimbulkan
kebisingan. Salah satu ciri mesin 4 tak adalah tekanan kompresinya. Jika
bahan bakar berupa gas yang dimampatkan, akan lebih banyak
energi yang dilepaskan. Gagasan ini pertama kali dikembangkan oleh
Alphone Beau de Rochas 1815– 1891 yang berkewarganegaraan
Prancis, tetapi justru Otto yang menyukseskan ide tersebut.
Sumber: Jendela Iptek: Energi, 1997
Mudah dan Aktif Belajar Fisika untuk Kelas XI
192
6?EBED =2EC:EC 6C:? C6=2=E 66B=E2? EC292 =E2B 282B 52A2D 6:?5292? 2=B 52B: D6A2D H2?8 36BCE9E B6?529 6 D6A2D H2?8
36BCE9ED:?88:6C:?C6A6BD::?:5:C63ED6C:?A6?5:?8:?:C2=?H2=62B: 6C 52? A6?5:?8:? BE2?82? 2D2E
- + +-
1. Proses Reversibel dan Irreversibel
BC6CABC6CA2526C:?2=B252H2?836BC:72D -1-.52?252AE=2
H2?8 36BC:72D --1-. D:52 B6F6BC:36= BC6C -1-. 6BEA22?
ABC6CH2?836B=2?8CE?8C2?82D=232DC69:?882ABC6C?H252A2D5:2?882A C63282: B2?82:2? 62522? C6D:32?8 ,6=EBE9 ABC6C D6BC63ED 52A2D
5:6B;22?C642B2632=:2?D2?A26?8E32936C2BEC292H2?85:=2E2? 2D2E 2=B H2?8 5:A:?5292?
BC6CB6F6BC:36=C6AEB?2D:5252A2D5:D6?DE2?52=26?H2D22?2B6?2 ABC6C:?:D2D6B32D2CBC6C:?:;E826?896?52:D:52252?H286C62?
82?88E2? 2=:B2? E52B2 C6BD2 72DB A6?8E329 2=B 52? EC292 =2:??H2 BC6C H2?8 252 A252 6?H2D22??H2 252=29 ABC6C :BB6F6BC:36= 252
ABC6C ?H2D2 :C2=?H2 2C:9 5:D6E2? 86C62? H2?8 6?H63232? 252?H2 A2?2C H2?8 9:=2?8 2D2E 2=:B2? 82C H2?8 36BE329
2. Mesin Pendingin Refrigerator
EE-6B5:?2:236BA682?86A252646?56BE?82?2=2:29 C:72D2=BH2?8C6=2=E6B232DC642B2CA?D2?52B:36?5236BCE9ED:?88:
636?52H2?836BCE9EB6?52964E2=:;:2252EC292=E2BH2?862C2 6:?5292? 2=B 52B: C:CD6 36BCE9E B6?529 6 =:?8E?82? H2?8
36BCE9E =63:9 D:?88: 252 6C:? A6?5:?8:? C:CD6 6?823:= 2=B
52?6=6A2C2?2=B 52AE?EC292H2?85:=2E2?252=29
,:=EC 6C:? A6?5:?8:? 52A2D 5:=:92D A252 .2
6D6B2?82? 8232B 2=B H2?8 5:=6A2C2? A252 CE9E D:?88:
2=BH2?85:C6B2AA252CE9EB6?529 EC292 H2?8 5:=2E2? 52B: =E2B
.EB2? 52H2 C63E29 6C:? A6?5:?8:? 5:?H2D22? 56?82? 67:C:6? 52H2 8E?2 ,642B2 2D62D:C 52A2D 5:DE=:C2? C63282: 36B:ED
O 62B:6C52?A6?5:?8:?BE2?82?6:=::67:C:6?52H28E?252=2
;2?82E2?C2A2:56?82?,62:?D:?88:?:=2: C62:?32:6C:?
A6?5:?8:? D6BC63ED
W Q
1
T
1
Q
2
T
2
Gambar 8.15
Perubahan kerja menjadi kalor.
Tantangan
untuk Anda
Mengapa AC menggunakan freon? Apakah freon dapat
digantikan oleh gas lain?
-6A6B2DEB5:52=2C63E29=62B:6C252=29O
L=E:526B;2H2?85:2A2D2? 5:52=2?H26?8632?8A252D6A6B2DEBC636C2BL-6?DE2?=2967:C:6?
52H28E?2=62B:6CD6BC63ED 7
:6D29E: O
6?82?6?88E?22?A6BC222?
Contoh
8.9
