PHYS102 Previous Exam Problems. Temperature, Heat & The First Law of Thermodynamics

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1 PHYS102 Previus Exam Prblems CHAPTER 18 Temperature, Heat & The First Law f Thermdynamics Equilibrium & temperature scales Thermal expansin Exchange f heat First law f thermdynamics Heat cnductin 1. The vlume f 1.00 kg water is mm 3 at a temperature f 10.0 C and mm 3 at a temperature f C. Calculate the cefficient f vlume expansin fr water in that range f temperature. (Ans: / C ) 2. An islated rd is in thermal cntact with a ht reservir at ne end and with a cld reservir at ther end (figure 1). The rd cnsists f a 1.00-m sectin f cpper jined by a sectin f length L2 f steel. Bth rds have the same crss sectinal area f 4.00 cm 2. The temperature f the cpper-steel junctin T j is 65 C. Assume steady state, find L 2. [k steel = 14 W/m.K; k cu = 401 W/m.K] (Ans: m) 3. Hw much ice at C must be mixed with 0.25 kg f water, initially at 20.0 C, t btain a final temperature f mixture f 0.0 C with all ice melted? [c ice = 2220 J/kg K] (Ans: 56 g) 4. A square hle 8.00 cm alng each side is cut in a sheet f metal. If the temperature f the sheet is increased 2 by 50 K, the area f the hle increases by 0.11 cm. Find the cefficient f linear expansin α f the metal. (Ans: C -1 ) 5. Helium cndenses int the liquid phase at apprximately 4 K. What is the crrespnding temperature in degrees Fahrenheit? (Ans: - 452) 6. A gas is cmpressed frm 600 cm 3 t 200 cm 3 at a cnstant pressure f 400 kpa. At the same time, 100 J f heat is transferred ut f gas. What is change in the internal energy f the gas during this prcess? (Ans: 60 J) 7. A 15-g ice cube at 0 C is placed in an aluminum cup whse initial temperature is 70 C. The system cmes t an equilibrium temperature f 20 C. What is the mass f the cup? [c Al = 900 J/kg.K, L f-ice = 333 kj/kg.k] (Ans: 140 g) 8. Tw cylindrical cpper rds, with different lengths L1 and L 2 and different diameters D 1 and D 2, are cnnected acrss tw heat reservirs with temperatures T L = 0 C and T H =100 C, as shwn in figure 2. In steady state, the heat cnductin rate thrugh the rd L 1 is half f that thrugh L 2. If L 1 = 40 cm, D 2 = 1.2 D 1, what is the length L 2? [k cpper = 385 W/m.K] (Ans: 29 cm) 9. A glass flask with vlume 250 cm 3 is filled with mercury at 25 C. Hw much mercury verflws when the temperature f the system is raised t 105 C? [α glass = K -1 and β mercury = K -1 ] (Ans: 3.4 cm 3 ) 10. A metal rd has a length f 7.30 m at 15 C and a length f 7.40 m at 95 C. What is the temperature f the rd when its length is 7.21 m? (Nte: take Ti = 15 C) (Ans: -57 C) Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 1

2 g f ice at 0 C is mixed with 100 g f water at 70 C, what is the final temperature f the mixture? (Ans: 0 C) 12. Figure 3 shws five slabs f different materials with equal thickness and same crss sectinal area, placed side by side. Heat flws frm left t right and steady state temperatures are given at the interfaces. Which slab has largest thermal cnductivity? (Ans: 3) 13. A steel rd is cm in diameter at 35 C. A brass ring has an inner diameter f cm at 35 C. At what cmmn temperature will the brass ring slide nt steal rd? [α steel = /K -1, α brass = /K - 1 ] (Ans: 286 C) 14. What mass f steam initially at 100 C shuld be mixed with 160 g f ice at 0 C in a thermally insulated cntainer t prduce liquid water at 40 C? (Ans: 32 g) 15. A 20-kg blck f cpper is drpped and falls 122 m. Calculate the rise in the temperature f the blck if all the ptential energy lst in the fall is cnverted t heat. [specific heat f cpper = 386 J/kg.K] (Ans: 3.1 K) 16. Figure 4 shws a steel bar 15 cm lng welded end t end t a cpper bar 30 cm lng. Each bar has a square crss sectinal area f 2.2 cm 2. The free end f steel is maintained at 100 C and the free end f cpper is maintained at 0.0 C. Find the temperature at the junctin f the tw bars, assuming steady state. [ksteel = 50.2 W/m.K, k cpper = 385 W/m.K] (Ans: 21 C) 17. A 2.0-cm diameter cylinder cntains 50 ml f water at 10.0 C. What is the change in the water level when the temperature rises t 80 C? Ignre the change in the vlume f the tube. [β water = / C, and 1 ml = 1 cm 3 ] (Ans: 0.23 cm) g f steam at 100 C lse J f heat. Calculate the final temperature? [Heat f vaprizatin f water is J/kg, heat f fusin is 333 kj/kg, and the specific heat f water = 4.19 kj/kg K] (Ans:75 C ) 19. The temperature f ne side f an 8.0-mm thick glass windw is maintained at 45 C while the ther side is maintained at 25 C. If the area f the windw is 2.0 m 2, hw much energy is transferred thrugh the windw in 5 hurs? [k glass = 1.0 W/m K] (Ans: J) 20. Figure 5 shws an aluminum and an irn rds jint tgether. The rds have the same crss sectin and their sides are insulated. In steady state, find the temperature T3 at the far end f the irn rd. [k Al = 235 W/mK and k irn = 14 W/mK] (Ans: 302 C) 21. An irn ball has a diameter f 6.00 cm and is 0.01 cm larger than the diameter f a brass ring. Bth are at a temperature f 20 C. T what temperature shuld the brass ring be heated s that the ball just passes thrugh the hle? [α brass = K -1 ] (Ans: 108 C) 22. A persn wants t cl 0.3 kg f water that is initially at 30 C by adding ice initially at -25 C. Hw much ice shuld he add s that the final temperature will be 0 C, with all the ice melted? [Fr ice, use the specific heat = J/ (kg.k), and heat f fusin = J/kg] (Ans: 99 g) 23. In a p-v diagram, a system f an ideal gas ges thrugh the prcess shwn in figure 6. Hw much heat is absrbed after the system ges thrugh this cycle 10 times. [Take P = 1.0 Pa and V = 1.0 m ] (Ans: 20 J) 24. It is recmmended t use a new temperature scale called Z. On the Z scale, the biling pint f water is 65.0 Z and the freezing pint is Z. T what temperature n the Fahrenheit scale wuld a temperature f -100 Z crrespnd? [Nte: bth scales are linear] (Ans: -159 F) 3 Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 2

3 25. Fifty grams f ice at 0 C is placed in a therms bttle cntaining 100 grams f water at 6.0 C. Hw many grams f ice will melt? (Ans: 7.5 g) 26. A cylinder with a frictinless pistn cntains 0.2 kg f water at 100 C. What is the change in the internal energy f water when it is cnverted t steam at 100 C at a cnstant pressure f 1 atm. [ρ steam = 0.6 kg/m 3, ρ water = 10 3 kg/m 3 ] (Ans: 418 kj) 27. Cnsider a cpper slab f thickness L and area f 5.0 m 2. If the cnductin rate thrugh the cpper slab is J/s and the temperature n the left f the slab is 102 C while n the right f the slab it is C, what must be the thickness f the slab? [k cpper = 400 W/(m.K)] (Ans: 19 cm) 28. Calculate the amunt f energy required t cmpletely melt 130 g f lead initially at temperature f 15.0 C. [Melting pint f lead = 328 C, latent heat f fusin f lead = J/kg, and the specific heat f lead = 128 J/kg.K] (Ans: J) 29. When the temperature f a metal sphere is raised by 75 C, the sphere s vlume increases by m 3. If the riginal vlume is m 3, find the cefficient f linear expansin f the sphere. (Ans: /C ) 30. Liquid nitrgen bils at a temperature f -196 C when the pressure is ne atmsphere. A silver cin f mass 15 g and temperature 25 C is drpped int the liquid. What mass f nitrgen bils ff as the cin cls t 196 C? [Take the specific heat f silver = 235 J/Kg/K, and latent heat f vaprizatin fr liquid nitrgen is J/Kg] (Ans: 3.9 g) 31. Hw much heat is required t melt ice f mass 500 g at -10 C t water at 0 C? [specific heat f ice: c = 2220 J/(kg.K); heat f fusin f ice: L f = J/kg] (Ans: J) 32. A steel washer (ring) has an inner diameter f cm and an uter diameter f cm at 20 C. T what temperature must the washer be heated t just fit ver a rd that is cm in diameter? [αsteel = / C] (Ans: 247 C) 33. A cylindrical cpper rd f length 1.5 m and crss sectinal area 6.5 cm 2 is insulated t prevent heat lss thrugh its surface. The ends are maintained at a temperature difference f 100 C by having ne end in a waterice mixture and the ther in biling water and steam. Hw much ice is melted per hur at the cld end? [thermal cnductivity f cpper = 401 W/(m.K); heat f fusin f ice L f = J/kg] (Ans: 188 g) 34. The cefficient f linear expansin f gld is /K. If the density f gld is g/cm 3 at 20 C, what will be the density f gld at 90 C? (Ans: g/cm 3 ) 35. A thermmeter, f mass 0.06 kg and specific heat 836 J/kg.K, reads 15 C. It is then cmpletely immersed in 0.15 kg f water f specific heat 4180 J/kg.K. The final temperature reading f the thermmeter in the water is 45 C. Assuming n heat lsses frm the system t the surrunding, what was the initial temperature f the water? (Ans: 47.4 C) 36. At what reading d the Fahrenheit and Kelvin scales agree? (Ans: 574) 37. A lead bullet, traveling at 200 m/s, strikes a tree and cmes t rest. If half the heat prduced is retained by the bullet. What will be the change in the temperature f the bullet? Assume that all the kinetic energy is cnverted t heat energy. [specific heat f lead = J/kg. C] (Ans: 80 C ) 38. Cnsider a steel plate with area 2.0 m 2 at 20 C. What is the magnitude f the change in its area when the temperature is lwered t -20 C? [cefficient f linear expansin f steel = / C] (Ans: m 2 ) Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 3

4 39. Cpper pellets, each f mass 1.0 g, are heated t 100 C. Hw many pellets must be added t 500 g f water initially at 20 C t make the final equilibrium temperature 30 C? [Neglect the heat capacity f the cntainer, specific heat f cpper = cal/g. C, and specific heat f water = 1.0 cal/g. C] (Ans: 773) 40. A gas expands frm a vlume f 2.00 m 3 t a vlume f 6.00 m 3 alng tw different paths, as shwn in figure 7. The heat added t the gas alng path IAF equals J. Find the heat added during path IF. (Ans: J) 41. Tw cntainers A and B, each having 1.0 kg f water, are initially at 20 C. Cntainer A is heated by 10 K, while cntainer B is heated by 10 F. Then, they are mixed. What is the final temperature? (Ans: 27.8 C) 42. In the p-v diagram shwn in figure 8, 150 J f heat is added t the system in prcess AB, and 600 J f heat is added t the system in prcess BD. What is the ttal heat added in prcess ACD? (Ans: 600 J) 43. Tw steel rds are each m lng at 20.0 C. Their ends are 1.00 mm apart, as shwn in figure 9. T what cmmn temperature shuld they be heated s that their ends tuch at pint A? [α steel = / C] (Ans: 111 C) 44. Heat flws thrugh a slab. It takes 1.0 minute t transfer 600 J f thermal energy acrss the slab. If the slab thickness is dubled, its crss-sectinal area is halved, and the temperature difference acrss it is dubled, hw lng will it take t transfer the same amunt f thermal energy? (Ans: 120 s) 45. A gas within a clsed chamber is taken thrugh the cycle shwn in the p-v diagram f figure 10. Calculate the net energy added as heat, and the change in the internal energy f the gas per cycle. (Ans: Q = -120 J, E int = 0) 46. A clsed cubical bx (60 cm n edge and 5 cm n thickness) cntains ice at 0 C. When the utside temperature is 20 C, it is fund that 250 grams f ice melt each hur. What is the thermal cnductivity f the walls f the bx? (Ans: W/m.K) 47. Hw much water remains unfrzen after 50.2 kj is transferred as heat frm 260 g f liquid water initially at 0 C? (Ans: 109 g) 48. A rm has a windw made f tw layers f glass separated by an air layer as in figure 11. Each f the 3 layers has a thickness f 0.50 mm and an area f 1.0 m 2. The temperature utside the rm is - 20 C, while the temperature inside the rm is + 20 C. What is the rate f heat transfer by cnductin thrugh the windw? Assume steady state. [k glass = 1.0 W/m.K, k air = W/m.K] (Ans: 2.0 kw) 49. The heat lst by 300 g f a metal as it cls by 50.0 C raises the temperature f 300 g f water by 10.0 C. The specific heat f water is 4190 J/kg K. What is the specific heat f the metal? (Ans: 838 J/kg.K) 50. A blck f 200 g f cpper is drpped int a cntainer that has 500 g f water. Bth are at a temperature T = 90 C. The system is left t cl dwn slwly. What is the temperature f the system when the heat lst by the water and the cpper is J? Neglect any heat gained r lst by the cntainer. The specific heats f water and cpper are 4180 J/kg K and 386 J/kg.K, respectively. (Ans: 81 C) 51. A 2.00-kg sample f steam at 100 C lses 2.26 kj f heat. What is the final temperature f the sample? (Ans: 100 C) 52. Heat is cnducted by tw cylindrical rds, cnnected in series, with identical crss sectinal area and length, as shwn in figure 12. One f the rds is made f carbn; the ther is made f silver. Find the rati f the cnductin rate f the silver rd t the cnductin rate f the carbn rd in a steady state cnditin. [κ 440W/m.K, κ carbn = 1100 W/m.K] (Ans: 1.00) Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 4 silver =

5 53. Heat is cnducted by tw cylindrical rds with identical crss sectinal area and length (see figure 13). The temperature difference between the ends f each rd is the same. One f the rds is made f carbn, while the ther is made f silver. What is the rati f the cnductin rate f the silver rd t the cnductin rate f the carbn rd? [κ silver = 440W/m.K, κ carbn = 1100 W/m.K] (Ans: 0.40) 54. Find the change in vlume f an aluminum sphere, with an initial radius f 0.1 m, when it is heated frm 0.0 C t 100 C. [α Al = / C] (Ans: 29 cm 3 ) 55. A bridge is made frm segments f cncrete that are 50 m lng each. If the linear expansin cefficient f cncrete is / C, hw much spacing is needed t allw fr expansin fr an extreme change in temperature f 150 F? (Ans: 5.0 cm) 56. Tw metal rds, ne silver and the ther cpper, each is 5.00 cm lng and has a square crss-sectin 2.00 cm n a side. As shwn in figure 14, bth rds are cnnected in parallel between a steam chamber at a temperature f 100 C, at ne end, and an ice-water bath, with a temperature f 0 C, at the ther. Hw much heat flws thrugh the tw rds in 1.00 minute? [κsilver = 417, κ cpper = 395 W/(m K)] (Ans: 39.0 kj) 57. A steel ball has a radius f 10 cm at 20 C. What is the magnitude f the change in its vlume when the temperature is lwered t 20 C? [α steel = / C]. (Ans: m 3 ) 58. One end f a cylindrical rd f length 50.0 cm and crss sectinal area 11.5 cm 2 is placed in a steam bath at 100 C whereas the ther end is inserted int an ice bath at 0 C. If 500 g f ice melts in 30.0 min, what is the rd made up f? (Ans: Cpper: (k = 402 W/m.K)) kg f steam at 100 C is mixed with 1.00 kg f ice at 0 C. Assuming the system is islated, what is the final temperature f the mixture? (Ans: 100 C) 60. When the average temperature f the earth increases by 1.00 C, cmmnly knwn as glbal warming, by what percentage will the vlume f the cean due t expansin be increased? [β = / C ] (Ans: 0.02%) 61. Five grams f ice at 0 C is placed in an insulated cntainer having 100 grams f water at 100 C. What is the final temperature f the mixture? (Ans: 91.4 C) 62. At 20 C, a brass cube has an edge length f 10 cm. What is the increase in the cube s ttal surface area when it is heated frm 20 C t 75 C? [αbrass = /K] (Ans: 1.3 cm 2 ) 63. The melting pint f sulfur is C, and is F belw its biling pint. Determine the biling pint f sulfur in degrees Celsius. (Ans: C) 64. A metallic rd has a length f 60 cm. One end is maintained at 80 C and the ther end is at 20 C. In steady state, what is the temperature f the rd at a pint which is 20 cm frm the ht end? (Ans: A 200-g ice cube at 0.0 C is drpped int 350 g f water at 20 C. What is the temperature f the mixture when it reaches thermal equilibrium? (Ans: 0.0 C) 66. A steel rd is placed between tw parallel walls, as shwn in figure 16. At 20 C, the rd has a length f 3.5 m and is separated by 1.0 mm frm each wall. The rd is heated unifrmly. At what temperature will it tuch bth walls? The cefficient f linear expansin f steel is 11 x 10-6 C -1. (Ans: 72 C) 67. The specific heat f bject B is twice that f bject A, and the mass f bject A is three times the mass f bject B. Initially A is at 300 K, and B is at 450 K. They are placed in thermal cntact with each ther and the cmbinatin is islated. What is the final temperature f bth bjects? (Ans: 360 K) C) Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 5

6 68. The change in the internal energy f an ideal gas as it mves frm a t c alng the path abc is -300 J (see figure 18). As it mves frm c t d, 280 J is transferred t it as heat. As the gas mves frm d t a, it absrbs 110 J as heat. Hw much wrk is dne by the gas as it mves frm c t d? (Ans: +90 J) 69. A cubic tank filled with 5.0 kg f water is insulated frm all sides except its tp which is cvered with a square glass sheet f length 2.0 m and thickness 3.0 cm. The water is initially at 20 C. It is expsed fr 20 secnds t the utside envirnment where the temperature is 55 C. Find the change in the temperature f water (assume that heat is distributed unifrmly in the water). (k glass = 1.0 W/m.K) (Ans: 4.5 C ) A B C D E Cnceptual Prblems 1. A bar f cpper is heated frm 280 K t 300 K. Which f the fllwing statements is nt true? A. Its density will increase slightly. B. Its length will increase slightly. C. Its electrical resistance will increase slightly. D. Its mass will remain unchanged. E. Its weight will remain unchanged. 2. Which ne f the fllwing statements is wrng? A. Tw bdies can be in thermal cntact fr a very lng time withut being in thermal equilibrium. B. The density f mst substances decreases when they are heated. C. If tw bdies are in thermal equilibrium then they must have the same temperature. D. Generally, liquids expand mre than slids fr the same temperature change. E. Mst slid materials cntract when cled. 3. In a thermdynamic prcess, the internal energy f a system in a cntainer with adiabatic walls decreases by 800 J. Which f the fllwing statements is crrect? A. The system perfrmed 800 J f wrk n its surrundings. B. The system gained 800 J by heat transfer frm its surrundings. C. The system lst 800 J by heat transfer t its surrundings. D. The surrunding perfrmed 800 J f wrk n the system. E. The 800 J f wrk dne by the system was equal t the 800 J f heat transferred t the system frm its surrundings. 4. Specify the wrng statement. A. Tw bdies are in thermal equilibrium with each ther if their temperatures are different. B. A thermmeter is an instrument that measures temperature. C. Tw bdies in thermal equilibrium with a third, are in thermal equilibrium with each ther. D. If tw bdies are in thermal cntact, they can have initially different temperatures. E. Celsius, Fahrenheit and Kelvin are three temperature scales. Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 6

7 5. Bdy A is at higher temperature than Bdy B. When they are placed in cntact, heat will flw frm A t B A. until bth have the same temperature. B. nly if the specific heat f A is larger than that f B. C. nly if the vlume f A is larger than that f B. D. nly if A has the greater internal energy cntent. E. nly if the thermal cnductivity f A is greater than that f B. 6. Tw different materials have the same mass and are at the same initial temperature. Equal quantities f energy are absrbed as heat by each. Their final temperature may be different because they have different: A. specific heat. B. cefficients f expansin. C. densities. D. thermal cnductivities. E. vlumes. 7. Which f the fllwing statements is true? A. If tw bjects are in thermal equilibrium they must have the same temperature. B. 272 K is warmer than 0 C. C. If an bject (A) is warmer than a secnd bject (B) in the Fahrenheit scale, then bject (B) must be warmer than bject (A) in the Celsius scale. D. When the temperature f an bject increases by ne C, it means that it has increased by less than ne F. E. The cefficient f linear expansin is the same fr all materials. 8. Which f the fllwing statements is wrng? A. If wrk is dne n a system, the internal energy f the system decreases in an adiabatic prcess. B. In an adiabatic prcess, transfer f energy as heat is zer. C. In a cnstant-vlume prcess, the internal energy f the system increases if heat is added. D. In a cyclic prcess, the change in internal energy f the system is zer. E. Heat energy can be transferred nly between bdies having different temperatures. 9. Which ne f the fllwing statements is crrect? A. Temperatures which differ by 10 n the Celsius scale must differ by 18 n the Fahrenheit scale. B. Temperatures differing by 25 n the Fahrenheit scale must differ by 45 n the Celsius scale. C. 40 K crrespnds t 40 C. D. Water at 96 C is warmer than water at 212 F. E. 0 F crrespnds t 32 C. 10. In a certain prcess, a gas ends in its riginal thermdynamic state. Of the fllwing, which is pssible as the net result f the prcess? A. The gas absrbs 50 J f energy as heat and des 50 J f wrk. B. It is adiabatic and the gas des 50 J f wrk. C. The gas des n wrk but absrbs 50 J f energy as heat. D. The gas des n wrk but rejects 50 J f energy as heat. E. The gas rejects 50 J f heat and des 50 J f wrk. Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 7

8 11. On a cld winter day, metallic bjects generally feel cler t the tuch than wden bjects. This is because: A. metals cnduct heat better than wd. B. a given mass f wd cntains mre heat than the same mass f metal. C. heat tends t flw frm metal t wd. D. the equilibrium temperature f metal is lwer than that f wd. E. the mass density f wd is less than the mass density f metals. 12. A system underges an adiabatic prcess in which its internal energy increases by 20 J. Which f the fllwing crrectly describes changes in the system? A. Heat: nne, Wrk: 20 J n the system B. Heat: nne, Wrk: 20 J by the system C. Heat: 20 J remved, Wrk: nne D. Heat: 20 J added, Wrk: nne E. Heat: 40 J added, Wrk: 20 J by the system 13. In a certain cyclic prcess a gas ends in its initial thermdynamic state. Which ne f the fllwing statements is pssible as the net result f the prcess? A. The gas absrbs 50 J f heat and des 50 J f wrk. B. The gas absrbs 50 J f heat and 50 J f wrk is dne n it. C. The gas absrbs 100 J f heat and des 50 J f wrk. D. The gas rejects 100 J f heat and des 100 J f wrk. E. The gas des n wrk but absrbs 100 J f heat. 14. Yu take a blck f ice at 0 C and add heat t it at a steady rate. It takes time t t cmpletely cnvert the blck f ice t steam at 100 C. What d yu have at time t/2? A. A mixture f water and steam at 100 C. B. All ice at 0 C. C. Water at a temperature between 0 C and 100 C. D. A mixture f ice and water at 0 C. E. All steam at 100 C. 15. A metallic bullet, f mass m and specific heat c, hits a steel plate with speed v. During the impact, 50% f the bullet s initial kinetic energy is cnverted t thermal energy in the bullet. What is the rise in the temperature f the bullet? A. v 2 /(4c) 2 B. v /(2c) C. v/(4c) D. v 2 /(c) E. v/(2c) 16. Which f the fllwing statements are crrect? 1. The first law f thermdynamics represents the cnservatin f energy. 2. Rm temperature is abut 20 degrees n the Kelvin scale. 3. A calrie is apprximately 4.2 J. 4. Heat has the same units as wrk. 5. Heat is a temperature difference. A. 1, 3, and 4 B. 2 and 4 C. 1, 2, and 3 D. 3 and 5 E. 1 and 5 Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 8

9 17. Which f the fllwing statements is FALSE regarding the prcesses cnnecting the same pints i and f shwn in the three diagrams in figure 15? A. Change in internal energy is different in all three prcesses B. Wrk is different in all three prcesses C. Heat energy transfer is different in all three prcesses D. The first law f thermdynamics can be applied t the three prcesses E. The wrk is psitive in all three prcesses 18. Which f the fllwing statements are WRONG? 1. Tw bjects are in thermal equilibrium if they have the same temperature. 2. In an isthermal expansin, the wrk dne by the gas is equal t the change in its internal energy. 3. In an adiabatic prcess, heat lst by the gas is equal t the wrk dne n the gas. 4. In an ischric prcess, heat exchanged is equal t the change in internal energy f the gas. A. 2 and 3 B. 1 and 2 C. 1 and 3 D. 1 and 4 E. 2 and Cnsider the cyclic prcess shwn in figure 17. If Q BC is negative and ( E int ) CA is negative, which f the fllwing statement is CORRECT? A. Q B. Q C. Q D. Q E. Q AB AB BC CA net is psitive is negative is psitive is psitive = A sample f a gas underges a transitin frm an initial state i t a final state f by tw different paths, if and ibf, as shwn in figure 19. The energy transferred t the gas as heat alng the path if is 10 piv i. Find the change in internal energy f the gas fr the path ibf. A. 6 piv B. piv C. (3/2) piv i i D. 10 piv E. (5/2) piv i i i 21. Tw rds, made f different materials but having the same length and diameter, are welded end t end between tw thermal reservirs, as shwn in figure 20. In steady state, what is the temperature (T ) at the junctin between the tw rds? A. 100 k1/( k 1 + k 2 ) B. 100 k2/( k 1 + k 2 ) C. 100 k1 k 2/( k 1 + k 2 ) D. 50 k1/( k 1 + k 2 ) E. 50 k2/( k 1 + k 2) x Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 9

10 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 10

11 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Dr. M. F. Al-Kuhaili PHYS 102 Chapter 18 Page 11