List of top Physics Questions on Thermodynamics

The ratio of molar specific heats of oxygen is

1 mole gas at standard pressure and at 27°C temperature is heated such that its volume and pressure both become doubled. The final temperature will be

An ideal monatomic gas follows the ABCDA path in the adjoining P-V diagram. The work done by the gas will be

A real gas within a closed chamber at $ 27^\circ \text{C} $ undergoes the cyclic process as shown in the figure. The gas obeys the equation $ PV^3 = RT $ for the path A to B. The net work done in the complete cycle is (assuming $ R = 8 \, \text{J/molK} $):

A mixture of one mole of monoatomic gas and one mole of diatomic gas (rigid) are kept at room temperature ($ 27^\circ \text{C} $). The ratio of specific heat of gases at constant volume respectively is:

Two vessels $ A $ and $ B $ are of the same size and are at the same temperature. Vessel $ A $ contains $ 1 \, \text{g} $ of hydrogen and vessel $ B $ contains $ 1 \, \text{g} $ of oxygen. $ P_A $ and $ P_B $ are the pressures of the gases in $ A $ and $ B $ respectively. Then $ \frac{P_A}{P_B} $ is:

The efficiency of a Carnot engine operating between a reservoir and an sink is $ \eta $. If the temperature of the reservoir is increased by 50% and that of the sink is decreased by 50%, the new efficiency will be:

A system goes from state a to b along the path abc, when 20 kJ of heat flows into the system and the system does 7.6 kJ of work. If the system is returned back from b to a along the curved path bca due to a work of 5 kJ done on it, then

The ratio of specific heats $ \frac{C_P}{C_V} $ in terms of degrees of freedom (n) is given by:

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio of $\frac{C_p}{C_v}$ for the gas is :

Given below are two statements:
Statement 1: If a capillary tube is immersed first in cold water and then in hot water, the height of capillary rise will be smaller in hot water.
Statement 2: If a capillary tube is immersed first in cold water and then in hot water, the height of capillary rise will be smaller in cold water.
In the light of the above statements, choose the most appropriate option from the options given below:

Match List I with List II

Choose the correct answer from the options given below :

The specific heat at constant pressure of a real gas obeying $ PV^2 = RT $ equation is:

A total of 48 J heat is given to one mole of helium kept in a cylinder. The temperature of helium increases by $2^\circ C$. The work done by the gas is: (Given, $R = 8.3 \, \text{J K}^{-1} \, \text{mol}^{-1}$).

Two different adiabatic paths for the same gas intersect two isothermal curves as shown in the $P-V$ diagram. The relation between the ratio $\frac{V_a}{V_d}$ and the ratio $\frac{V_b}{V_c}$ is:

A diatomic gas ($ \gamma = 1.4 $) does 100 J of work in an isobaric expansion. The heat given to the gas is:

Water boils in an electric kettle in 20 minutes after being switched on. Using the same main supply, the length of the heating element should be ………….. to …………. times of its initial length if the water is to be boiled in 15 minutes.

A sample of 1 mole gas at temperature T is adiabatically expanded to double its volume. If adiabatic constant for the gas is $\gamma=\frac{3}{2}$ , then the work done by the gas in the process is:

An observer is standing below a freely falling source of sound of frequency 900 Hz. The change in the frequency noticed by the observer after 3 seconds of free fall of the source is (speed of sound in air is 330 ms$^{-1}$ and acceleration due to gravity = 10 ms$^{-2}$)

At a pressure $ P $ and temperature $ 127^\circ C $, a vessel contains 21 g of a gas. A small hole is made into the vessel so that the gas leaks out. At a pressure of $ \frac{2P}{3} $ and a temperature of $ t^\circ C $, the mass of the gas leaked out is 5 g. Then $ t $ is:

The temperature difference between the ends of two cylindrical rods A and B of the same material is $ 2:3 $. In steady state, the ratio of the rates of flow of heat through the rods A and B is $ 5:9 $. If the radii of the rods A and B are in the ratio $ 1:2 $, then the ratio of lengths of the rods A and B is?

The temperatures of the source and sink of a Carnot’s heat engine are 27$^\circ$C and 127$^\circ$C respectively. If the absolute temperature of the sink is decreased by 10%, the efficiency of the engine:

The temperatures of the source and sink of a Carnot’s heat engine are 27$^\circ$C and 127$^\circ$C respectively. If the absolute temperature of the sink is decreased by 10\%, the efficiency of the engine:

The efficiency of a reversible heat engine working between two temperatures is 50\%. The coefficient of performance of a refrigerator working between the same two temperatures but in reverse direction is:

The total internal energy of 4 moles of a diatomic gas at a temperature of $27^\circ C$ is: (Universal gas constant $ R = 8.31 \, \text{J mol}^{-1} \text{K}^{-1} $)