TERMODINAMIKA Departemen Fisika Fakultas Matematika dan Ilmu Pengetahuan Alam Institut Pertanian Bogor
Latihan Satu mol gas ideal yang mula-mula ada pada tekanan 1 atm dan suhu 0°C ditekan secara isotermis dan kuasi statik sehingga tekanannya menjadi 2 atm. Hitung (a) volume gas mula-mula, (b) usaha yang diperlukan untuk menekan gas (c) panas yang dikeluarkan gas selama proses kompresi tersebut.
2. Sebuah mesin kalor bekerja pada dua isobarik (105Pa dan 3×105Pa) dan dua isokhorik (0,5 L dan 2 L). (a) Gambarkan siklus mesin tersebut dalam diagram p-V. (b) Hitung kerja yang dihasilkan mesin tiap siklus.
3. Sebuah mesin Carnot bekerja pada suhu 400 K dan 900 K 3. Sebuah mesin Carnot bekerja pada suhu 400 K dan 900 K. (a) tentukan efisiensi mesin. Jika kalor yang diserap sistem pada tandon suhu tinggi adalah 5000 J tiap siklusnya, tentukan (b) kalor yang dibuang sistem pada tandon suhu rendah (c) kerja yang dilakukan sistem tiap siklus.
4. Satu mol gas ideal mula-mula mengalami ekspansi bebas dari V1 = 12,3 L dan T1 = 300 K sampai V2 = 24,6 L dan T2 = 300 K. Gas ini kemudian dikompresi secara isotermal dan kuasi statik kembali ke keadaan semula. (a) berapakah perubahan entropi semesta untuk satu siklus yang lengkap? (b) berapakah usaha yang terbuang dalam siklus ini?
5. An engine operates with 1 mol of an ideal gas, for which Cv = 3/2R and Cp = 5/2R, as its working substance. The cycle begins at P1 = 1 atm and V1 = 24.6 L. The gas is heated at constant volume to P2 = 2 atm. It then expands at constant pressure until V2 = 49.2 L. During these two steps, heat is absorbed by the gas. The gas is then cooled at constant volume until its pressure is again 1 atm. It is then compressed at constant pressure to its original state. During the last two steps, heat is rejected by the gas. All the steps are quasi-static and reversible. (a) Show this cycle on a PV diagram. Find the work done, the heat added, and the change in the internal energy of the gas for each step of the cycle. (b) Find the efficiency of the cycle.
6. One mole of an ideal monatomic gas at an initial volume V1 = 25 L follows the cycle shown in Figure. All the processes are quasistatic. Find (a) the temperature of each state of the cycle, (b) the heat flow for each part of the cycle, and (c) the efficiency of the cycle
7. Two moles of a diatomic gas are carried through the cycle ABCDA shown in the PV diagram in Figure. The segment AB represents an isothermal expansion, the segment BC an adiabatic expansion. The pressure and temperature at A are 5 atm and 600 K. The volume at B is twice that at A. The pressure at D is 1 atm. (a) What is the pressure at B? (b) What is the temperature at C? (c) Find the work done by the gas in one cycle and the thermodynamic efficiency of this cycle.