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1 Reg. No. :... Code No. : 0863 Sub. Code : GMPH B.Sc. (CBCS) DEGREE EXAMINATION, NOVEMBER 016. Second Semester Physics Main THERMAL PHYSICS (For those who joined in July ) Time : Three hours Maximum : 75 marks PART A (10 1 = 10 marks) Answer ALL questions. Choose the correct answer : 1. öμúõàm Âv i P T when V = (A) õô¼ (B) õô¼ CÀø» (C) JÊ[PõP õö (D) GxªÀø» By Ragnault s law P T when V is (a) constant (b) not constant (c) uniform change (d) none

2 Ws. Áõ²Âß AÊzu P = (A) (C) 1/ 3c (B) 1/3 c 1 / (D) 1 / 3 c The pressure exerted by a gas P = (a) 1 / 3c (b) 1/3 c (c) 1 / (d) 1 / 3 c 3.»UTÔß \μõ\ õu¼øh yμ m (A) (B) 10 (C) 8 10 (D) 8 10 The mean free path of a molecule is about m (a) 7 10 (b) 7 10 (c) 8 10 (d) Áõ²Âß õq À ußø (A) T (B) T 1/ (C) T (D) Coefficient of velocity of gas 1/ 1 T (a) T (b) T 1/ (c) T (d) 1/ 1 T Page Code No. : 0863

3 5. J ]ìhzvà EÒÍ BØÓÀ öuõs (A) öáî BØÓÀ (B) EÒ BØÓÀ (C) BØÓÀ (D) GxªÀø» The energy content of a system is called its (a) external energy (b) internal energy (c) energy (d) none 6. vóß (A) ( Q1 Q )/ Q1 (B) ( Q1 Q )/ Q1 (C) Q / ) (D) Q / ) ( 1 Q Efficiency ( Q1 (a) ( Q1 Q )/ Q1 (b) ( Q1 Q )/ Q1 (c) Q / ) (d) Q / ) ( 1 Q ( Q1 7. PõºÚõm Gg]Ûß vóß = (A) 1 T /T1 (B) 1 T 1 /T (C) T /T1 (D) T 1/T The efficiency of the carnot's engine = (a) 1 T /T1 (b) 1 T 1 /T (c) T /T1 (d) T 1/T Page 3 Code No. : 0863

4 Ws 8. RÌPshÁØÖÒ uà öá C UP ¾US öuõhº øh x Gx (A) öá (B) AÊzu (C) BØÓÀ (D)»UTÖ Out of the following the physical quantity that relates with first law of thermodynamics is (a) temperature (b) pressure (c) energy (d) molecule 9. \ AÊzu {ø» À uß öá HØ zvóß (A) '0' (B) +ve (C) ve (D) +ve or ve Specific heat of saturated vapour pressure (a) zero (b) +ve (c) ve (d) +ve or ve 10. CßöÁº\ß öá T i = (A) (C) a R (B) a (D) a Rb a b The inversion temperature (a) (c) a R Page 4 (b) a (d) T i = a Rb a b Code No. : 0863

5 PART B (5 5 = 5 marks) Answer ALL questions, choosing either (a) or (b). Answer should not exceeding 50 words. 11. (A) Uì öáà \ [S BØÓÀ Âv TÔ ÂÍUSP. State and explain Maxwell s law of equi partition of energy. (B) \μõ\ õu¼øh yμ ØÖ PõÍzvß uûzußø ØÔ ÂÁõv. Discuss about mean free path and sphere of influence. 1. (A) v, õ À ØÖ õö öá {ø» BQ ÁØÔØS Cøh EÒÍ öuõhºø ö ÖP. Obtain the relation between inversion, boyles and critical temperatures. (B) Áøμ Ö : (i) öá U PhzuÀ (ii) öá a\»ú (iii) öá Pvº Ãa_. Page 5 Code No. : 0863

6 Ws Define : (i) conduction (ii) convection (iii) radiation. 13. (A) \ öá {PÌÂÀ Áø»UPõÚ PõøÁ Á Â. Obtain an expression for the workdone during an isothermal process. (B) \ öá ØÖ öá õøõhøó {PÌøÁ Áøμ h» ÂÁ. Explain about the slope of isothermal and adabatic process. 14. (A) Kº º GvºÄÖ _ÇØ] À Gßm μõ _È GÚ {ÖÄP. Prove that for a reversible cycle change of entropy is zero. (B) Gßm μõ ß Ai øh UQ zxá ØÔ SÔ ÁøμP. Write a note on physical significance of entropy. Page 6 Code No. : 0863

7 15. (A) T-dS CμshõÁx \ ß õk Põs. Obtain the second T-dS equation. (B) UìöÁÀ¼ß ßÓõ öá  ¾UPõÚ \ ß õk Á Â. Derive Maxwell s third thermodynamic relation. PART C (5 8 = 40 marks) Answer ALL questions, choosing either (a) or (b). Answer should not exceeding 600 words. 16. (A) BUê\ß»UTÖ 7ºC C US õx Auß rms vø\ ÁP Psk i. Calculate the rms velocity of oxygen molecule at 7 degree centigrade. (B) Áõ² HØ kzx AÊzuzvØPõÚ PõøÁ Põs. Arrive an expression for the pressure exterted by a gas. Page 7 Code No. : 0863

8 Ws 17. (A) Áõ² C UP À öpõòøp i õq À GsoØPõÚ PõøÁ Põs. Derive an expression for the coefficient of velocity on the basis of kinetic theory of gas. (B) Áõ² C UP À öpõòøp i öá UPhzx GsoØPõÚ PõøÁ Á Â. On the basis of Kinetic theory of gases arrive an expression for the coefficient of thermal conductivity of gases. 18. (A) Áõ²ÄUS EshõÚ öá õøôhøó \ ß õk Á Â. Obtain the adiabatic equation for a perfect gas. (B) \ öá õøó ØÖ öá õøõhøó õøó CμskUS EÒÍ Áø»UPõÚ PõøÁ Á Â. Arrive an expression for the work done during an isothermal and adiabatic process. Page 8 Code No. : 0863

9 19. (A) QÍõ] À QÍ μõß \ ß õmøh Á  dp dt L. T V V 1 Establish the Clausius Clapeyron s equation. dp dt L. T V V 1 (B) J Põº Úõ Gg]ß 0ºC ØÖ 100ºC US Cøh ¾ ØÖ öá C vμzvß ºGvºÄÓõ {PÌÂÀ 17ºC ØÖ 7ºC US Cøh Áø» ö\ ² õx GvÀ AvP vóß GÚ Psk i. Which has the greatest efficiency (i) a Carnot s engine working between 0ºC and 100ºC (ii) a reversible heat engine works between 17ºC and 7ºC. Page 9 Code No. : 0863

10 Ws 0. (A) öá C UP ¾UPõÚ öuõhº ¼ x C p 9T Cv GÚU Põs. KT From the thermodynamical relation show 9T that Cp Cv. KT (B) öá C UP ¼ß ªßÚÊzuzvØPõÚ Uì öáàì öuõhºø Á Â. Derive Maxwell relation from thermodynamic potential. Page 10 Code No. : 0863