Thermodynamics (Physics)

An electric heater supplies heat to a system at a rate of 100 W. If the system performs work at a rate of 75 J/s, then the rate at which internal energy increases will be :

1. 75 W
2. 25 W
3. 100 W
4. 125 W

In an adiabatic expansion, the temperature of one mole of an ideal monatomic gas ( = 5/3) decreases from 60 K to 50 K. The work done by the gas in the process is: (Take the universal gas constant as R = 8.3 J mol-1 K-1)

1. 166 J
2. 41.5 J
3. 83 J
4. 124.5 J

One mole of an ideal monatomic gas undergoes a cyclic process as shown in the figure. The total heat supplied to the gas is: [figure]

1. 800 J
2. 400 J
3. 500 J
4. 600 J

Two gases A and B are filled at the same pressure in separate cylinders with movable pistons of radius rA and rB, respectively. On supplying an equal amount of heat to both the systems reversibly under constant pressure, the pistons of gas A and B are displaced by 16 cm and 9 cm, respectively. If the change in their internal energy is the same, then the ratio rArB is equal to

1. 2 3
2. 32
3. 43
4. 34

A thermodynamic system is taken through the cycle abcda. The work done by the gas along the path bc is: [figure]

1. Zero
2. 30 J
3. -90 J
4. -60 J

The equilibrium state of a thermodynamic system is described by Choose the most appropriate answer from the options given below.

1. A, B and E only
2. B, C and D only
3. A, B and C only
4. A, C and D only

A Carnot engine has an efficiency of 50\% when its source is at a temperature 327 . The temperature of the sink is :-

1. 15
2. 100
3. 200
4. 27

An ideal gas undergoes four different processes from the same initial state as shown in the figure below. Those processes are adiabatic, isothermal, isobaric and isochoric. The curve which represents the adiabatic process among 1, 2, 3 and 4 is [figure]

1. 1
2. 2
3. 3
4. 4

An ideal gas follows a process described by the equation PV2 = C from the initial (P1, V1, T1) to final (P2, V2, T2) thermodynamic states, where C is a constant. Then

1. If P1 > P2 then V1 > V2
2. If P1 > P2 then T1 < T2
3. If V2 > V1 then T2 > T1
4. If V2 > V1 then T2 < T1

Two cylinders A and B of equal capacity are connected to each other via a stop cock. A contains an ideal gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is :

1. adiabatic
2. isochoric
3. isobaric
4. isothermal

In which of the following processes, heat is neither absorbed nor released by a system?

1. adiabatic
2. isobaric
3. isochoric
4. isothermal

A sample of 0.1 g of water at 100°C and normal pressure (1.013 105 N m-2) requires 54 cal of heat energy to convert to steam at 100°C. If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is

1. 104.3 J
2. 208.7 J
3. 42.2 J
4. 84.5 J

The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state A to state B, is [figure]

1. 25
2. 23
3. 13
4. 27

The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is

1. 26.8%
2. 20%
3. 6.25%
4. 12.5%

Thermodynamic processes are indicated in the following diagram. [figure] Match the following

1. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
2. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
3. (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
4. (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)

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. 99 J
3. 100 J
4. 1 J

A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then

1. Compressing the gas isothermally or adiabatically will require the same amount of work.
2. Which of the case (whether compression through isothermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.
3. Compressing the gas isothermally will require more work to be done.
4. Compressing the gas through adiabatic process will require more work to be done.

A refrigerator works between 4 and 30 . It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is (Take 1 cal = 4.2 Joules)

1. 236.5 W
2. 2365 W
3. 2.365 W
4. 23.65 W

One mole of an ideal monatomic gas undergoes a process described by the equation PV3 = constant. The heat capacity of the gas during this process is

1. 32 R
2. 52 R
3. 2R
4. R

The temperature inside a refrigerator is t2 C and the room temperature is t1 C. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

1. t1t1 - t2
2. t1 + 273t1 - t2
3. t2 + 273t1 - t2
4. t1 + t2t1 + 273

An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas ?

1. Isochoric
2. Isothermal
3. Adiabatic
4. Isobaric

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