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Page 1 JEE Solved Example on Calorimetry and Thermal Expansion JEE Mains Q1: Overall change in volume and radii of a uniform cylindrical steel wire are ?? . ?? % and ?? . ?????? % respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is (?? = ?? . ?? × ???? ???? ???? -?? ) (A) ?? . ?? × ???? ?? ???? -?? (B) ?? . ?? × ???? ?? ???? -?? (C) ?? . ?? × ???? ?? ???? -?? (D) ?? . ???? × ???? ?? ???? -?? Ans: (D) ?? = ?? × ?? ? ???? ?? = ???? ?? + ?? l l ? 0.2 100 = -2 × ???? ?? + ?? l l ? ?? l l = 0.2 100 - ( -2 × 0.002 100 ) ?? l l = 0.2 + 0.004 100 ? 0.204 100 So stress = ?? × strain = 2 × 10 11 × 0.204 100 = 4.08 × 10 8 N/m 2 . Q2: A solid sphere of radius R made of material of bulk modulus ?? is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass ?? is placed on the piston to compress the liquid, the fractional change in the radius of the sphere ???? /?? is (A) Kmg /A (B) ?????? /?? ?? (C) ???? /?? (D) ???? /?????? Ans: (B) 1 K = -1.?V V ?p and ?P = mg A So ??? ?? = ???? ?? = 4?? ?? 2 · ???? 4?? 3 ?? 3 = 3???? ?? = ???? 3???? = ???? ?? After correction Page 2 JEE Solved Example on Calorimetry and Thermal Expansion JEE Mains Q1: Overall change in volume and radii of a uniform cylindrical steel wire are ?? . ?? % and ?? . ?????? % respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is (?? = ?? . ?? × ???? ???? ???? -?? ) (A) ?? . ?? × ???? ?? ???? -?? (B) ?? . ?? × ???? ?? ???? -?? (C) ?? . ?? × ???? ?? ???? -?? (D) ?? . ???? × ???? ?? ???? -?? Ans: (D) ?? = ?? × ?? ? ???? ?? = ???? ?? + ?? l l ? 0.2 100 = -2 × ???? ?? + ?? l l ? ?? l l = 0.2 100 - ( -2 × 0.002 100 ) ?? l l = 0.2 + 0.004 100 ? 0.204 100 So stress = ?? × strain = 2 × 10 11 × 0.204 100 = 4.08 × 10 8 N/m 2 . Q2: A solid sphere of radius R made of material of bulk modulus ?? is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass ?? is placed on the piston to compress the liquid, the fractional change in the radius of the sphere ???? /?? is (A) Kmg /A (B) ?????? /?? ?? (C) ???? /?? (D) ???? /?????? Ans: (B) 1 K = -1.?V V ?p and ?P = mg A So ??? ?? = ???? ?? = 4?? ?? 2 · ???? 4?? 3 ?? 3 = 3???? ?? = ???? 3???? = ???? ?? After correction Q3: A cylindrical wire of radius ?? ???? , length ?? ?? , Young's modulus = ?? × ???? ???? ???? ?? , Poisson's ratio ?? = ?? /???? is stretched by a force of ?????? ?? . Its radius will become (A) ?? . ?????????? ???? (B) ?? . ?????????? ???? (C) ?? . ?????????? ???? (D) ?? . ?????????? ???? Ans: (D) Stress = ?? × Strain ? Strain = Stress /?? = 100 ?? ?? 2 × 1 2 × 10 11 = 1 2 × 10 9 × 3.14 × 10 -6 = 1 6.28 × 10 3 = 10 6.28 × 10 -4 = 1.6 × 10 -4 Now, ?? · dl l = -dr r ? dr = -1 mm× ?? × dl l = -1.6 × 10 -4 × 3.14 10 , ?? - ?? 0 = -5.024× 10 -5 Q4: A block of mass ?? . ?? ???? is heated to a temperature of ?????? ° ?? and placed a large ice block. What is the maximum amount of ice that can melt (approx.)? Specific heat for the body = ?? . ???????? /???? ° ?? . (A) ?? ???? (B) ?? . ?? ???? (C) ?? ???? (D) ?? . ?? ???? Ans: (B) 2.5 × 10 3 gm· (0.1cal/gm ° C) · (500- 0) = m × L ? 2.5 × 100× 0.1 × 500 80 = m. = 1.5625× 10 3 g Q?? : ?? ???? of ice at- ???? ° ?? is mixed with ?? . ?? ???? of water at ???? ° ?? . The final temperature of mixture is: (specific heat of ice is ???????? ?? /???? /?? ) (A) ?? . ?? ° ?? (B) ?? . ?? ° ?? (C) ?? . ?? ° ?? (D) ?? . ?? ° ?? Ans: (D) 1cal = 4.2 J ? Specific heat of ice = 21000 42 cal/Kg· K = 500cal /kg. K = 0.5cal/gm· K Page 3 JEE Solved Example on Calorimetry and Thermal Expansion JEE Mains Q1: Overall change in volume and radii of a uniform cylindrical steel wire are ?? . ?? % and ?? . ?????? % respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is (?? = ?? . ?? × ???? ???? ???? -?? ) (A) ?? . ?? × ???? ?? ???? -?? (B) ?? . ?? × ???? ?? ???? -?? (C) ?? . ?? × ???? ?? ???? -?? (D) ?? . ???? × ???? ?? ???? -?? Ans: (D) ?? = ?? × ?? ? ???? ?? = ???? ?? + ?? l l ? 0.2 100 = -2 × ???? ?? + ?? l l ? ?? l l = 0.2 100 - ( -2 × 0.002 100 ) ?? l l = 0.2 + 0.004 100 ? 0.204 100 So stress = ?? × strain = 2 × 10 11 × 0.204 100 = 4.08 × 10 8 N/m 2 . Q2: A solid sphere of radius R made of material of bulk modulus ?? is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass ?? is placed on the piston to compress the liquid, the fractional change in the radius of the sphere ???? /?? is (A) Kmg /A (B) ?????? /?? ?? (C) ???? /?? (D) ???? /?????? Ans: (B) 1 K = -1.?V V ?p and ?P = mg A So ??? ?? = ???? ?? = 4?? ?? 2 · ???? 4?? 3 ?? 3 = 3???? ?? = ???? 3???? = ???? ?? After correction Q3: A cylindrical wire of radius ?? ???? , length ?? ?? , Young's modulus = ?? × ???? ???? ???? ?? , Poisson's ratio ?? = ?? /???? is stretched by a force of ?????? ?? . Its radius will become (A) ?? . ?????????? ???? (B) ?? . ?????????? ???? (C) ?? . ?????????? ???? (D) ?? . ?????????? ???? Ans: (D) Stress = ?? × Strain ? Strain = Stress /?? = 100 ?? ?? 2 × 1 2 × 10 11 = 1 2 × 10 9 × 3.14 × 10 -6 = 1 6.28 × 10 3 = 10 6.28 × 10 -4 = 1.6 × 10 -4 Now, ?? · dl l = -dr r ? dr = -1 mm× ?? × dl l = -1.6 × 10 -4 × 3.14 10 , ?? - ?? 0 = -5.024× 10 -5 Q4: A block of mass ?? . ?? ???? is heated to a temperature of ?????? ° ?? and placed a large ice block. What is the maximum amount of ice that can melt (approx.)? Specific heat for the body = ?? . ???????? /???? ° ?? . (A) ?? ???? (B) ?? . ?? ???? (C) ?? ???? (D) ?? . ?? ???? Ans: (B) 2.5 × 10 3 gm· (0.1cal/gm ° C) · (500- 0) = m × L ? 2.5 × 100× 0.1 × 500 80 = m. = 1.5625× 10 3 g Q?? : ?? ???? of ice at- ???? ° ?? is mixed with ?? . ?? ???? of water at ???? ° ?? . The final temperature of mixture is: (specific heat of ice is ???????? ?? /???? /?? ) (A) ?? . ?? ° ?? (B) ?? . ?? ° ?? (C) ?? . ?? ° ?? (D) ?? . ?? ° ?? Ans: (D) 1cal = 4.2 J ? Specific heat of ice = 21000 42 cal/Kg· K = 500cal /kg. K = 0.5cal/gm· K So suppose the mixture is at temperature ?? , then ?? ?? · ?? ?? · (??? ) + ?? ?? ?? = +?? ?? · ?? ?? (?? - 0) = ?? ?? · ?? ?? (30 - ?? ) ? 1000× 0.5 × 10 + 80 × 1000+ 1000× 1 × ?? = 4400× 1 × (30 - ?? ) ? 5000+ 80000+ 1000 T = 4400× 30 - 4400 T ? 5400 T = 47000 ? T = 8.7 ° C Q6: Steam at ?????? ° ?? is added slowly to ???????????? of water at ???? ° ?? , until the temperature of water is raised to ???? ° ?? . The mass of steam required to do this is (?? ?? = ???????????? /???? ): (A) ?????????? (B) ?????????? (C) ?????????? (D) ?????????? Ans: (?? )???? ??? = ?? ?? · ?? ?? ? 1400× 1 × 64 = ?? × 540 Q7: Ice at ?? ° ?? is added to ?????? ?? of water initially at ???? ° ?? in a vacuum flask. When ???? ?? of ice has been added and has all melted the temperature of the flask and contents is ???? ° ?? . When a further ???? ?? of ice has been added and has all melted, the temperature of the whole is ???? ° ?? . Calculate the specific latent heat of fusion of ice. [? Takes ?? = ???????? /???? ° ?? ] (A) ?? . ?? × ???? ?? ?? /???? (B) ?? . ?? × ???? ?? ?? /???? (C) ?? . ?? × ???? ?? ?? /???? (D) ?? . ?? × ???? ?? ?? /???? Ans: (A) Let the heat capacity of the flask be M Then ?? = latent heat of fusion Then 50?? + 50(40 - 0) = 200× (70 - 40) + (70 - 40) × ?? ? 50?? + 2000= 6000+ 30M ? 5?? = 3?? + 400 And 80 L + 80(10 - 0) = 250× (40 - 10) + ?? (30) Page 4 JEE Solved Example on Calorimetry and Thermal Expansion JEE Mains Q1: Overall change in volume and radii of a uniform cylindrical steel wire are ?? . ?? % and ?? . ?????? % respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is (?? = ?? . ?? × ???? ???? ???? -?? ) (A) ?? . ?? × ???? ?? ???? -?? (B) ?? . ?? × ???? ?? ???? -?? (C) ?? . ?? × ???? ?? ???? -?? (D) ?? . ???? × ???? ?? ???? -?? Ans: (D) ?? = ?? × ?? ? ???? ?? = ???? ?? + ?? l l ? 0.2 100 = -2 × ???? ?? + ?? l l ? ?? l l = 0.2 100 - ( -2 × 0.002 100 ) ?? l l = 0.2 + 0.004 100 ? 0.204 100 So stress = ?? × strain = 2 × 10 11 × 0.204 100 = 4.08 × 10 8 N/m 2 . Q2: A solid sphere of radius R made of material of bulk modulus ?? is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass ?? is placed on the piston to compress the liquid, the fractional change in the radius of the sphere ???? /?? is (A) Kmg /A (B) ?????? /?? ?? (C) ???? /?? (D) ???? /?????? Ans: (B) 1 K = -1.?V V ?p and ?P = mg A So ??? ?? = ???? ?? = 4?? ?? 2 · ???? 4?? 3 ?? 3 = 3???? ?? = ???? 3???? = ???? ?? After correction Q3: A cylindrical wire of radius ?? ???? , length ?? ?? , Young's modulus = ?? × ???? ???? ???? ?? , Poisson's ratio ?? = ?? /???? is stretched by a force of ?????? ?? . Its radius will become (A) ?? . ?????????? ???? (B) ?? . ?????????? ???? (C) ?? . ?????????? ???? (D) ?? . ?????????? ???? Ans: (D) Stress = ?? × Strain ? Strain = Stress /?? = 100 ?? ?? 2 × 1 2 × 10 11 = 1 2 × 10 9 × 3.14 × 10 -6 = 1 6.28 × 10 3 = 10 6.28 × 10 -4 = 1.6 × 10 -4 Now, ?? · dl l = -dr r ? dr = -1 mm× ?? × dl l = -1.6 × 10 -4 × 3.14 10 , ?? - ?? 0 = -5.024× 10 -5 Q4: A block of mass ?? . ?? ???? is heated to a temperature of ?????? ° ?? and placed a large ice block. What is the maximum amount of ice that can melt (approx.)? Specific heat for the body = ?? . ???????? /???? ° ?? . (A) ?? ???? (B) ?? . ?? ???? (C) ?? ???? (D) ?? . ?? ???? Ans: (B) 2.5 × 10 3 gm· (0.1cal/gm ° C) · (500- 0) = m × L ? 2.5 × 100× 0.1 × 500 80 = m. = 1.5625× 10 3 g Q?? : ?? ???? of ice at- ???? ° ?? is mixed with ?? . ?? ???? of water at ???? ° ?? . The final temperature of mixture is: (specific heat of ice is ???????? ?? /???? /?? ) (A) ?? . ?? ° ?? (B) ?? . ?? ° ?? (C) ?? . ?? ° ?? (D) ?? . ?? ° ?? Ans: (D) 1cal = 4.2 J ? Specific heat of ice = 21000 42 cal/Kg· K = 500cal /kg. K = 0.5cal/gm· K So suppose the mixture is at temperature ?? , then ?? ?? · ?? ?? · (??? ) + ?? ?? ?? = +?? ?? · ?? ?? (?? - 0) = ?? ?? · ?? ?? (30 - ?? ) ? 1000× 0.5 × 10 + 80 × 1000+ 1000× 1 × ?? = 4400× 1 × (30 - ?? ) ? 5000+ 80000+ 1000 T = 4400× 30 - 4400 T ? 5400 T = 47000 ? T = 8.7 ° C Q6: Steam at ?????? ° ?? is added slowly to ???????????? of water at ???? ° ?? , until the temperature of water is raised to ???? ° ?? . The mass of steam required to do this is (?? ?? = ???????????? /???? ): (A) ?????????? (B) ?????????? (C) ?????????? (D) ?????????? Ans: (?? )???? ??? = ?? ?? · ?? ?? ? 1400× 1 × 64 = ?? × 540 Q7: Ice at ?? ° ?? is added to ?????? ?? of water initially at ???? ° ?? in a vacuum flask. When ???? ?? of ice has been added and has all melted the temperature of the flask and contents is ???? ° ?? . When a further ???? ?? of ice has been added and has all melted, the temperature of the whole is ???? ° ?? . Calculate the specific latent heat of fusion of ice. [? Takes ?? = ???????? /???? ° ?? ] (A) ?? . ?? × ???? ?? ?? /???? (B) ?? . ?? × ???? ?? ?? /???? (C) ?? . ?? × ???? ?? ?? /???? (D) ?? . ?? × ???? ?? ?? /???? Ans: (A) Let the heat capacity of the flask be M Then ?? = latent heat of fusion Then 50?? + 50(40 - 0) = 200× (70 - 40) + (70 - 40) × ?? ? 50?? + 2000= 6000+ 30M ? 5?? = 3?? + 400 And 80 L + 80(10 - 0) = 250× (40 - 10) + ?? (30) ? 80 L + 800 = 7500+ 30M ? 8 L = 3M + 670 ? 8 L = 5 L - 400 + 670 ? L = 90cal/gm ? 90 × 4.2 × 10 3 J/kg = 3.8 × 10 5 J/Kg Q8: A continuous flow water heater (geyser) has an electrical power rating = ?????? and efficiency of conversion of electrical power into heat = ???? %. If water is flowing through the device at the rate of ?????????? / ?????? , and the inlet temperature is ???? ° ?? , the outlet temperature will be. (A) ???? . ?? ° ?? (B) ???? . ?? ° ?? (C) ???? ° ?? (D) ???? ° ?? Ans: (B) ???? ???? = 100 cm 3 /sec ? ???? ???? = ?? · ???? ???? = 100gm /sec. Now, power used in heating = 2000× 0.8 = 1600 W. Now, power = d(ms?T) dt = s. ?T. dm dt Now assuming ??? is same So 1600= 100 1000 kg sec × 4200 J kg · K × ?T ? 1600× 10 4200 = ?T = 3.8 ° C. ? T - 10 ° = 3.8 ° ? T = 13.8 ° C(B) Q9: A steel tape gives correct measurement at ???? ° ?? . A piece of wood is being measured with the steel tape gives correct measurement at ???? ° ?? . A piece of wood is being measured with the steel tape at ?? ° ?? . The reading is ???? ???? on the tape, The real length of the given piece of wood must be: (A) ???? ???? (B) < ???? ???? (C) > ???? ???? (D) Cannot say Ans: (B) Refer theory Page 5 JEE Solved Example on Calorimetry and Thermal Expansion JEE Mains Q1: Overall change in volume and radii of a uniform cylindrical steel wire are ?? . ?? % and ?? . ?????? % respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is (?? = ?? . ?? × ???? ???? ???? -?? ) (A) ?? . ?? × ???? ?? ???? -?? (B) ?? . ?? × ???? ?? ???? -?? (C) ?? . ?? × ???? ?? ???? -?? (D) ?? . ???? × ???? ?? ???? -?? Ans: (D) ?? = ?? × ?? ? ???? ?? = ???? ?? + ?? l l ? 0.2 100 = -2 × ???? ?? + ?? l l ? ?? l l = 0.2 100 - ( -2 × 0.002 100 ) ?? l l = 0.2 + 0.004 100 ? 0.204 100 So stress = ?? × strain = 2 × 10 11 × 0.204 100 = 4.08 × 10 8 N/m 2 . Q2: A solid sphere of radius R made of material of bulk modulus ?? is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass ?? is placed on the piston to compress the liquid, the fractional change in the radius of the sphere ???? /?? is (A) Kmg /A (B) ?????? /?? ?? (C) ???? /?? (D) ???? /?????? Ans: (B) 1 K = -1.?V V ?p and ?P = mg A So ??? ?? = ???? ?? = 4?? ?? 2 · ???? 4?? 3 ?? 3 = 3???? ?? = ???? 3???? = ???? ?? After correction Q3: A cylindrical wire of radius ?? ???? , length ?? ?? , Young's modulus = ?? × ???? ???? ???? ?? , Poisson's ratio ?? = ?? /???? is stretched by a force of ?????? ?? . Its radius will become (A) ?? . ?????????? ???? (B) ?? . ?????????? ???? (C) ?? . ?????????? ???? (D) ?? . ?????????? ???? Ans: (D) Stress = ?? × Strain ? Strain = Stress /?? = 100 ?? ?? 2 × 1 2 × 10 11 = 1 2 × 10 9 × 3.14 × 10 -6 = 1 6.28 × 10 3 = 10 6.28 × 10 -4 = 1.6 × 10 -4 Now, ?? · dl l = -dr r ? dr = -1 mm× ?? × dl l = -1.6 × 10 -4 × 3.14 10 , ?? - ?? 0 = -5.024× 10 -5 Q4: A block of mass ?? . ?? ???? is heated to a temperature of ?????? ° ?? and placed a large ice block. What is the maximum amount of ice that can melt (approx.)? Specific heat for the body = ?? . ???????? /???? ° ?? . (A) ?? ???? (B) ?? . ?? ???? (C) ?? ???? (D) ?? . ?? ???? Ans: (B) 2.5 × 10 3 gm· (0.1cal/gm ° C) · (500- 0) = m × L ? 2.5 × 100× 0.1 × 500 80 = m. = 1.5625× 10 3 g Q?? : ?? ???? of ice at- ???? ° ?? is mixed with ?? . ?? ???? of water at ???? ° ?? . The final temperature of mixture is: (specific heat of ice is ???????? ?? /???? /?? ) (A) ?? . ?? ° ?? (B) ?? . ?? ° ?? (C) ?? . ?? ° ?? (D) ?? . ?? ° ?? Ans: (D) 1cal = 4.2 J ? Specific heat of ice = 21000 42 cal/Kg· K = 500cal /kg. K = 0.5cal/gm· K So suppose the mixture is at temperature ?? , then ?? ?? · ?? ?? · (??? ) + ?? ?? ?? = +?? ?? · ?? ?? (?? - 0) = ?? ?? · ?? ?? (30 - ?? ) ? 1000× 0.5 × 10 + 80 × 1000+ 1000× 1 × ?? = 4400× 1 × (30 - ?? ) ? 5000+ 80000+ 1000 T = 4400× 30 - 4400 T ? 5400 T = 47000 ? T = 8.7 ° C Q6: Steam at ?????? ° ?? is added slowly to ???????????? of water at ???? ° ?? , until the temperature of water is raised to ???? ° ?? . The mass of steam required to do this is (?? ?? = ???????????? /???? ): (A) ?????????? (B) ?????????? (C) ?????????? (D) ?????????? Ans: (?? )???? ??? = ?? ?? · ?? ?? ? 1400× 1 × 64 = ?? × 540 Q7: Ice at ?? ° ?? is added to ?????? ?? of water initially at ???? ° ?? in a vacuum flask. When ???? ?? of ice has been added and has all melted the temperature of the flask and contents is ???? ° ?? . When a further ???? ?? of ice has been added and has all melted, the temperature of the whole is ???? ° ?? . Calculate the specific latent heat of fusion of ice. [? Takes ?? = ???????? /???? ° ?? ] (A) ?? . ?? × ???? ?? ?? /???? (B) ?? . ?? × ???? ?? ?? /???? (C) ?? . ?? × ???? ?? ?? /???? (D) ?? . ?? × ???? ?? ?? /???? Ans: (A) Let the heat capacity of the flask be M Then ?? = latent heat of fusion Then 50?? + 50(40 - 0) = 200× (70 - 40) + (70 - 40) × ?? ? 50?? + 2000= 6000+ 30M ? 5?? = 3?? + 400 And 80 L + 80(10 - 0) = 250× (40 - 10) + ?? (30) ? 80 L + 800 = 7500+ 30M ? 8 L = 3M + 670 ? 8 L = 5 L - 400 + 670 ? L = 90cal/gm ? 90 × 4.2 × 10 3 J/kg = 3.8 × 10 5 J/Kg Q8: A continuous flow water heater (geyser) has an electrical power rating = ?????? and efficiency of conversion of electrical power into heat = ???? %. If water is flowing through the device at the rate of ?????????? / ?????? , and the inlet temperature is ???? ° ?? , the outlet temperature will be. (A) ???? . ?? ° ?? (B) ???? . ?? ° ?? (C) ???? ° ?? (D) ???? ° ?? Ans: (B) ???? ???? = 100 cm 3 /sec ? ???? ???? = ?? · ???? ???? = 100gm /sec. Now, power used in heating = 2000× 0.8 = 1600 W. Now, power = d(ms?T) dt = s. ?T. dm dt Now assuming ??? is same So 1600= 100 1000 kg sec × 4200 J kg · K × ?T ? 1600× 10 4200 = ?T = 3.8 ° C. ? T - 10 ° = 3.8 ° ? T = 13.8 ° C(B) Q9: A steel tape gives correct measurement at ???? ° ?? . A piece of wood is being measured with the steel tape gives correct measurement at ???? ° ?? . A piece of wood is being measured with the steel tape at ?? ° ?? . The reading is ???? ???? on the tape, The real length of the given piece of wood must be: (A) ???? ???? (B) < ???? ???? (C) > ???? ???? (D) Cannot say Ans: (B) Refer theory Q10: A metallic rod ?? ???? long with a square crosssection is heated through ?? ° ?? . If Young's modulus of elasticity of the metal is ?? and the mean coefficient of linear expansion is ?? per degree Celsius, then the compressional force required to prevent the rod from expanding along its length is: (Neglect the change of cross-sectional area) (A) EA ?? ?? (B) EA ???? (?? + ???? ) (C) ???????? (?? - ???? ) (D) ?? /???? Ans: (B) Actual length = ?? 0 (?? + ?? ??? ) = ?? 0 (1 + ???? ) Change in length = ?? 0 (1 + ?? t) - ?? 0 = ?? 0 ???? So strain = ?? 0 ???? ?? 0 (1+?? t) = ?? t (1+?? t) ? Stress = E × strain = E?? t (1+?? t) ? Force = A × stress = EA?? t 1+?? t Q11: A solid ball is completely immersed in a liquid. The coefficient of volume expansion of the ball and liquid are ?? × ???? -?? and ?? × ???? -?? per ° ?? respectively. The percentage change in upthrust when the temperature is increased by ?????? ° ?? is. (A) ?? . ?? % (B) ?? . ???? % (C) ?? . ?? % (D) ?? . ???? % Ans: (D) ?? l (t) · V s (t) · g = ?? l (1+8×10 -6 ×10 2 ) × v s (1 + 3 × 10 -6 × 10 2 ) × g = ?? l v s · g · (1 + 3 × 10 -4 )(1 - 8 × 10 -4 ) so difference = ?? l · v ?? · ?? (-5 × 10 -4 ) Q12: 70 cal of heat are required to raise the temperature of 2 mole of an ideal diatomic gas at constant pressure from ???? ° ?? . The amount of heat required (in calorie) to raise the temperature of the same gas through the same range (???? ° ?? to ???? ° ?? ) at constant volume is. (A) 30 (B) 50 (C) 70 (D) 90 Ans: (B) Q 1 = nC p ?T, Q 2 = nC v ?T, Q 2 Q 1 = ?? ?? ?? ?? = 1 ?? or Q 2 = Q 1 ?? = 70 1.4 = 50calRead More
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1. What is calorimetry and how is it used in thermal expansion? |
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