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Thermodynamics Quiz

Dear Readers,

Important topics for Thermodynamics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with the day-to-day experiences.

Q1. A gas does 4.5 J of external work during adiabatic expansion. If its temperature falls by 2K , its internal energy will:

•  Increase by 4.5 J
•  decrease by 4.5 J
•  decrease by 2.25 J
•  Increase by 9.0 J

Solution
Q=dU+dW In an adiabatic process, dQ=0 Hence dU=-dW=-4.5 J .

Q2.Two different adiabatic paths for the same gas intersect two isothermals at T_1 and T_2 as shown in the P-V diagram (Fig).

Then:

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Solution

  Q3For a gas, the difference between the two specific heats is 4150 J kg^(-1) K^(-1) and the ratio of the two specific heats is 1.4. What is the specific heat of the gas at constant volume in units of J kg^(-1) K^(-1)?:

•   8475
•   5186
•  1660
•  10375

Solution

Q4. Three moles of an ideal gas are taken through a cyclic process ABCA as shown on T-V diagram in Fig. The gas loses 2510 J of heat in the complete cycle. If T_A=100 K and T_B=200 K, The work done by the gas during the process BC is

•  5000 J
•  -5000 J
•  4000 J
•  -2500 J

Solution

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Q5. A thermally insulated rigid container contains an ideal gas at 27°C. It is fitted with a heating coil of resistance 50 Ω . A current is passed through the coil for 10 minutes by connecting it to a d. c. source of 10 V. The change in the internal energy is

•  Zero
•  300 J
•  600 J
•  1200 J

Solution
 

Q6. A Carnot’s engine whose sink is at a temperature of 300 K has an efficiency of 40%. By how much should the temperature of the source be increased so as to increase the efficiency to 60%?

•  250 K
•  275 K
• 300 K
•  325 K

Solution

Q7. Two monoatomic ideal gases 1 and 2 of molecular masses, M_1 and M_2 respectively are enclosed in separate containers kept at the same temperature. The ratio of the speed of sound in gas 1 to that in gas 2 is

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Solution

Q8. Figure shows a cyclic process ABCA in the V-T diagram. Which of the diagrams shown in Fig. shows the same process on a P-V diagram

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Solution

Q9. For a thermodynamic process, the P-V graph for a monoatomic gas is a straight line passing through the origin and having a positive slope. The molar heat capacity of the gas in this process is

•  R
•  2R
•  3/2*R
•  3R

Solution

Q10. An ideal gas (γ=1.4) expands from 5×10^(-3) m^3 to 25×10^(-3) m^3 at a constant pressure of 1×10^5Pa. The heat energy supplied to the gas in this process is

•  7 J
•  70 J
•  700 J
• 7000 J

Solution