Physics-DPP-1-4.First Law of Thermodynamics, Calorimetry and Heat Transfer

PHYSICS Topic: First Law of Thermodynamics, Calorimetry and Heat Transfer Date: 1. Work done by the gas in the process shown in figure is : (a) positive (b) negative (c) zero (d) may be positive or negative 2. One mole of a perfect gas in a cylinder fitted with a piston has a pressure P, volume V and temperature T. If the temperature is increased by 1 K keeping pressure constant, the increase in volume is : (a) 2V 273 V (b) 91 V (c) 273 Q (d) V 3. The molar heat capacity in a process of a diatomic gas if it does a work of 4 , when a heat of Q is supplied to it is : (a) 2 R (b) 5 R (c) 10 R (d) 6 R 5 2 3 7 4. In the cycle process ABCDA shown in the figure, consider the following statements : I. Area ABCD = Work done on the gas II. Area ABCD = Net heat absorbed III. Change in the internal energy in cycle = 0 which of these are correct : (a) I only (b) II only (c) II and III (d) I, II and III 5. A wall has two layers A and B, each made of different material. Both the layers have the same thickness. The thermal conductivity for A is twice that of B and, under steady condition, the temperature difference across the wall is 360C. The temperature difference across the layer A is : (a) 60C (b) 120C (c) 240C (d) 180C 6. A wall has two layers A and B each made of different materials. The layer A is 10 cm thick and B is 20 cm thick. The thermal conductivity of A is thrice that of B. Under thermal equilibrium temperature difference across the wall is 350C. the difference of temperature across the layer A is : (a) 200C (b) 100C (c) 150C (d) 50C 7. If a body coated black at 600 K surrounded by atmosphere at 300 K has cooling rate r0, the same body at 900 K, surrounded by the same atmosphere, will have cooling rate equal to : (a) 16 r (b) 8 r (c) 16r (d) 4r 3 0 16 0 0 0 8. Two rods of copper and brass (KC > K ) of same length and area of cross-section are joined as shown. End A is kept at 100 C and end 0 B at 00C. The temperature at the junction : (a) will be more than 500C (b) will be less than 500C (c) will be 500C (d) may be more or less than 500C depending upon the size of rods PHYSICS Topic: First Law of Thermodynamics, Calorimetry and Heat Transfer Date: 9. Three rods of same dimensions have thermal conductivites 3k, 2k and k. They are arranged as shown, with their ends at 1000C, 500C and 00C. The temperature of their junction is : (a) 750C (b) 200 0C 3 (c) 400C (d) 100 0 C 3 10. Three rods made of the same material and having same cross-sectional area but different lengths 10 cm, 20 cm and 30 cm are joined as shown. The temperature of the junction is : (a) 10.80C (b) 14.60C (c) 16.40C (d) 18.20C *** End of Paper *** PHYSICS Topic: First Law of Thermodynamics, Calorimetry and Heat Transfer Date: Answer Key 1. (b) 2. (c) 3. (c) 4. (c) 5. (b) 6. (d) 7. (a) 8. (a) 9. (b) 10. (c)