Thermodynamics (Physics) · Question 21

The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20 C, the temperature of the surroundings to which it rejects heat is

1. 11 C
2. 21 C
3. 31 C
4. 41 C

A Carnot engine, having an efficiency of = 110 as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is

1. 90 J
2. 1 J
3. 100 J
4. 99 J

One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure. [figure] The change in internal energy of the gas during the transition is

1. 20 J
2. -12 kJ
3. 20 kJ
4. -20 kJ

Figure below shows two paths that may be taken by a gas to go from a state A to a state C. [figure] In process AB, 400 J of heat is added to the system and in process BC, 100 J of heat is added to the system. The heat absorbed by the system in the process AC will be

1. 460 J
2. 300 J
3. 380 J
4. 500 J

A monatomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V. The final pressure of the gas is (Take = 5/3)

1. 64P
2. 32P
3. P/64
4. 16P

A thermodynamic system undergoes cyclic process ABCDA as shown in figure. The work done by the system in the cycle is [figure]

1. P0V0
2. 2P0V0
3. P0V02
4. zero

The molar specific heats of an ideal gas at constant pressure and volume are denoted by Cp and Cv, respectively. If = CpCv and R is the universal gas constant, then Cv is equal to

1. ( - 1)R
2. R
3. 1 + 1 -
4. R( - 1)

A gas is taken through the cycle A B C A, as shown. What is the net work done by the gas? [figure]

1. Zero
2. - 2000 J
3. 2000 J
4. 1000 J

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its temperature. The ratio of CpCv for the gas is

1. 53
2. 32
3. 43
4. 2

A system is taken from state a to state c by two paths adc and abc as shown in the figure. The internal energy at a is Ua = 10 J. Along the path adc the amount of heat absorbed dQ1 = 50 J and the work obtained dW1 = 20 J whereas along the path abc the heat absorbed dQ2 = 36 J. The amount of work along the path abc is [figure]

1. 10 J
2. 12 J
3. 36 J
4. 6 J