Thermodynamics (Physics) · Question 32

Two Carnot engines A and B are operated in series. The engine A receives heat from the source at temperature T1 and rejects the heat to the sink at temperature T. The second engine B receives the heat at temperature T and rejects to its sink at temperature T2. For what values of T the efficiencies of the two engines are equal

1. T1 - T22
2. T1T2
3. T1T2
4. T1 + T22

An ideal gas goes from state A to state B via three different processes as indicated in the P-V diagram. [figure] If Q1, Q2, Q3 indicate the heat absorbed by the gas along the three processes and U1, U2, U3 indicate the change in internal energy along the three processes respectively, then

1. Q1 > Q2 > Q3 and U1 = U2 = U3
2. Q3 > Q2 > Q1 and U1 = U2 = U3
3. Q1 = Q2 = Q3 and U1 > U2 > U3
4. Q3 = Q2 = Q1 and U1 > U2 > U3

One mole of an ideal gas goes from an initial state A to final state B via two processes : It first undergoes isothermal expansion from volume V to 3V and then its volume is reduced from 3V to V at constant pressure. The correct P-V diagram representing the two processes is

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A thermodynamic system is taken through the cycle ABCD as shown in figure. Heat rejected by the gas during the cycle is [figure]

1. 2PV
2. 4PV
3. 12PV
4. PV

A mass of diatomic gas ( = 1.4) at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 27 to 927 . The pressure of the gas in the final state is

1. 8 atm
2. 28 atm
3. 68.7 atm
4. 256 atm

During an isothermal expansion, a confined ideal gas does 150 J of work against its surroundings. This implies that

1. 150 J of heat has been removed from the gas
2. 300 J of heat has been added to the gas
3. no heat is transferred because the process is isothermal
4. 150 J of heat has been added to the gas

When 1 kg of ice at 0 melts to water at 0 , the resulting change in its entropy, taking latent heat of ice to be 80 cal/g, is

1. 273 cal/K
2. 8 104 cal/K
3. 80 cal/K
4. 293 cal/K

If cp and cv denote the specific heats (per unit mass) of an ideal gas of molecular weight M, then

1. cp - cv = RM2
2. cp - cv = R
3. cp - cv = RM
4. cp - cv = MR

A monatomic gas at pressure P1 and volume V1 is compressed adiabatically to 18th of its original volume. What is the final pressure of the gas?

1. 64P1
2. P1
3. 16P1
4. 32P1

If and represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

1. = - , in an adiabatic process
2. = , in an isothermal process
3. = , in an adiabatic process
4. = - , in an isothermal process