An ideal gas changes from state 'a' to state 'b' as shown in figure. What is the work done by the gas in the process?
1. zero
2. positive
3. negative
4. infinite
The temperature inside a refrigerator is and the room temperature is . The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be:
1.
2.
3.
4.
A refrigerator works between 4°C and 30°C. 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)23.65W
(2)236.5W
(3)2365W
(4)2.365W
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. 31°C
2. 41°C
3. 11°C
4. 21°C
If 150 J of heat is added to a system and the work done by the system is 110 J, then change in internal energy will be
(1) 260 J
(2) 150 J
(3) 110 J
(4) 40 J
In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas molecules absorb 30 J of heat and 10 J of work is done by the gas. If the initial internal energy of the gas was 40 J, then the final internal energy will be -
(1) 30 J
(2) 20 J
(3) 60 J
(4) 40 J
One mole of an ideal gas at an initial temperature of T K does 6R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of the gas will be:
1. (T + 2.4)K
2. (T – 2.4)K
3. (T + 4)K
4. (T – 4)K
We consider a thermodynamic system. If ΔU represents the increase in its internal energy and W the work done by the system, which of the following statements is true ?
1. ΔU = –W in an adiabatic process
2. ΔU = W in an isothermal process
3. ΔU = –W in an isothermal process
4. ΔU = W in an adiabatic process
For an adiabatic expansion of a perfect gas, the value of is equal to
(1)
(2)
(3)
(4)
Unit mass of a liquid with volume V1 is completely changed into a gas of volume V2 at a constant external pressure P and temperature T. If the latent heat of evaporation for the given mass is L, then the increase in the internal energy of the system is -
(1) Zero
(2)
(3)
(4) L
If the door of a refrigerator is kept open, then which of the following is true ?
1. Room is cooled
2. Room is heated
3. Room is either cooled or heated
4. Room is neither cooled nor heated
The temperature of reservoir of Carnot's engine operating with an efficiency of 70% is 1000K. The temperature of its sink is -
(1) 300 K
(2) 400 K
(3) 500 K
(4) 700 K
Efficiency of a Carnot engine is 50% when temperature of outlet is 500 K. In order to increase efficiency up to 60% keeping temperature of intake the same what is temperature of outlet ?
(1) 200 K
(2) 400 K
(3) 600 K
(4) 800 K
An ideal heat engine working between temperature T1 and T2 has an efficiency η, the new efficiency if both the source and sink temperature are doubled, will be
(1)
(2) η
(3) 2η
(4) 3η
An ideal refrigerator has a freezer at a temperature of –13°C . The coefficient of performance of the engine is 5. The temperature of the air (to which heat is rejected) will be
(1) 325°C
(2) 325K
(3) 39°C
(4) 320°C
An engine is supposed to operate between two reservoirs at temperature 727°C and 227°C. The maximum possible efficiency of such an engine is -
(1) 1/2
(2) 1/4
(3) 3/4
(4) 1
An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 × 104 cal of heat at higher temperature. Amount of heat converted to work is -
(1) 2.4 × 104 cal
(2) 6 × 104 cal
(3) 1.2 × 104 cal
(4) 4.8 × 104 cal
A monoatomic ideal gas, initially at temperature T1, is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature T2 by releasing the piston suddenly. If L1 and L2 are the lengths of the gas column before and after expansion respectively, then T1/ T2 is given by -
(1)
(2)
(3)
(4)
An ideal gas expands isothermally from a volume V1 to V2 and then compressed to original volume V1 adiabatically. Initial pressure is P1 and final pressure is P3. The total work done is W. Then -
(1)
(2)
(3)
(4)
An insulator container contains 4 moles of an ideal diatomic gas at temperature T. Heat Q is supplied to this gas, due to which 2 moles of the gas are dissociated into atoms but temperature of the gas remains constant. Then
1. Q = 2RT
2. Q = RT
3. Q = 3RT
4. Q = 4RT
The volume of air increases by 5% in its adiabatic expansion. The percentage decrease in its pressure will be -
(1) 5%
(2) 6%
(3) 7%
(4) 8%
The temperature of a hypothetical gas increases to times when compressed adiabatically to half the volume. Its equation can be written as
(1) PV3/2 = constant
(2) PV5/2 = constant
(3) PV7/3 = constant
(4) PV4/3 = constant
Two Carnot engines A and B are operated in succession. The first one, A receives heat from a source at T1 = 800 K and rejects to sink at T2 K. The second engine B receives heat rejected by the first engine and rejects to another sink at T3 = 300 K. If the work outputs of two engines are equal, then the value of T2 is -
(1) 100K
(2) 300K
(3) 550K
(4) 700K
Two samples A and B of a gas initially at the same pressure and temperature are compressed from volume V to V/2 (A isothermally and B adiabatically). The final pressure of A is
(1) Greater than the final pressure of B
(2) Equal to the final pressure of B
(3) Less than the final pressure of B
(4) Twice the final pressure of B
Initial pressure and volume of a gas are P and V respectively. First it is expanded isothermally to volume 4V and then compressed adiabatically to volume V. The final pressure of gas will be [Given : -
(1) 1P
(2) 2P
(3) 4P
(4) 8P
A thermally insulated rigid container contains an ideal gas heated by a filament of resistance 100 Ω through a current of 1A for 5 min . Then change in internal energy is -
(1) 0 kJ
(2) 10 kJ
(3) 20 kJ
(4) 30 kJ
A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62°C, the efficiency of the engine is doubled. The temperatures of the source and sink are -
(1) 80°C, 37°C
(2) 95°C, 28°C
(3) 90°C, 37°C
(4) 99°C, 37°C
An ideal gas of mass m in a state A goes to another state B via three different processes as shown in figure. If Q1, Q2 and Q3 denote the heat absorbed by the gas along the three paths, then -
(1) Q1 < Q2 < Q3
(2) Q1 < Q2 = Q3
(3) Q1 = Q2 > Q3
(4) Q1 > Q2 > Q3
A thermodynamic system is taken from state A to B along ACB and is brought back to A along BDA as shown in the PV diagram. The net work done during the complete cycle is given by the area
(1) P1ACBP2P1
(2) ACBB'A'A
(3) ACBDA
(4) ADBB'A'A
An ideal monoatomic gas is taken round the cycle as shown in following P-V diagram. The work done during the cycle is -
(1) PV
(2) 2 PV
(3) 4 PV
(4) Zero
A system changes from the state (P1, V1) to (P2, V2) as shown in the figure. What is the work done by the system ?
(1) 7.5 × 105 joule
(2) 7.5 × 105 erg
(3) 12 × 105 joule
(4) 6 × 105 joule
When a system is taken from state i to a state f along path iaf, Q = 50 J and W = 20 J.
If W = –13 J for the curved return path fi, Q for this path is -
1. 33 J
2. 23 J
3. – 7 J
4. – 43 J
An ideal gas is taken from point A to the point B, as shown in the P-V diagram. The work done in the process is -
1.
2.
3.
4.
Consider a process shown in the figure. During this process the work done by the system -
(1) Continuously increases
(2) Continuously decreases
(3) First increases, then decreases
(4) First decreases, then increases
Six moles of an ideal gas perform a cycle shown in figure. If the temperature are TA = 600 K, TB = 800 K, TC = 2200 K and TD = 1200 K, the work done per cycle is -
(1) 20 kJ
(2) 30 kJ
(3) 40 kJ
(4) 60 kJ
In the following figures, four curves A, B, C and D, are shown. The curves are:
1. | isothermal for A and D while adiabatic for B and C. |
2. | adiabatic for A and C while isothermal for B and D. |
3. | isothermal for A and B while adiabatic for C and D. |
4. | isothermal for A and C while adiabatic for B and D. |
In the following P-V diagram two adiabatics cut two isothermals at temperatures T1 and T2 (fig.). The value of will be
(1)
(2)
(3)
(4) VbVc
An ideal gas with adiabatic exponent undergoes a process in which work done by the gas is same as increase in internal energy of the gas. The molar heat capacity of gas for the process is –
1.
2.
3.
4.
The molar heat capacity for an ideal gas
1. cannot be negative
2. must be equal to either or
3. must lie in the range
4. may have any value between and
An ideal gas expands according to the law = const. The molar heat capacity C is :
1.
2.
3.
4.
The molar heat capacity C for an ideal gas going through a given process is given by C = a/T , where 'a' is a constant. If , the work done by one mole of gas during heating from to through the given process will be:
1.
2.
3.
4. none of these
One mole of a monoatomic ideal gas undergoes the process \(A\rightarrow B\) in the given \(P-V\) diagram. The molar heat capacity for this process is:
1. \(\frac{3R}{2}\)
2. \(\frac{13R}{6}\)
3. \(\frac{5R}{2}\)
4. \(2R\)
P-V diagram of a diatomic gas is straight line passing through origin. The molar heat capacity of the gas in the process will be
1. 4R
2. 2.5 R
3. 3R
4.
The pressure of a monoatomic gas increases linearly from N/m2 to N/m2 when its volume increases from 0.2 m3 to 0.5 m3. Calculate molar heat capacity of the gas [R = 8.31 J/mol k]
1. 20.1 J/molK
2. 17.14 J/molK
3. 18.14 J/molK
20.14 J/molK
At ordinary temperatures, the molecules of a diatomic gas have only translational and rotational kinetic energies. At high temperatures, they may also have vibrational energy. As a result of this compared to lower temperatures, a diatomic gas at higher temperatures will have:
1. | lower molar heat capacity. |
2. | higher molar heat capacity. |
3. | lower isothermal compressibility. |
4. | higher isothermal compressibility. |