Heat and Thermodynamics · Physics · NEET

The temperature of a metallic sphere of radius $R$ is increased by a small amount $\Delta T$. If the linear coefficient of thermal expansion of the metal is $\alpha$, the approximate increase in the volume of the sphere is:

In an adiabatic expansion, the temperature of one mole of an ideal monatomic gas ( $\gamma=5 / 3$ ) decreases from 60 K to 50 K . The work done by the gas in the process is:

(Take the universal gas constant as $R=8.3 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$ )

An ideal gas is made of polyatomic molecules. Each of the molecules has three translational, three rotational and $f$ number of vibrational modes. If the ratio of heat capacities $C_P / C_V$ of the gas is $8 / 7$, then the value of $f$ is:

The mean free path of molecules in an ideal gas $A$ is half that of another ideal gas $B$. The diameter of the spherical molecules of gas $A$ is twice the diameter of the molecules of $B$. If number densities of the gases $A$ and $B$ are $n_A$ and $n_B$, respectively, the correct option is:

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

A flask contains argon and chlorine in the ratio of $2: 1$ by mass. The temperature of the mixture is $27^{\circ} \mathrm{C}$. The ratio of root mean square speed of the molecules of the two gases $\left(\frac{V_{\mathrm{rms}}^{\mathrm{Ar}}}{V_{\mathrm{rms}}^{\mathrm{Cl}}}\right)$ is:

(Atomic mass of argon $=40.0 \mathrm{u}$ and molecular mass of chlorine $=70.0 \mathrm{u}$ )

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

Three identical heat conducting rods are connected in series as shown in the figure. The rods on the sides have thermal conductivity $2 K$ while that in the middle has thermal conductivity $K$. The left end of the combination is maintained at temperature $3 T$ and the right end at $T$. The rods are thermally insulated from outside. In steady state, temperature at the left junction is $T_1$ and that at the right junction is $T_2$. The ratio $T_1 / T_2$ is

A container has two chambers of volumes $V_1=2$ litres and $V_2=3$ litres separated by a partition made of a thermal insulator. The chambers contain $n_1=5$ and $n_2=4$ moles of ideal gas at pressures $p_1=1 \mathrm{~atm}$ and $p_2=2 \mathrm{~atm}$, respectively. When the partition is removed, the mixture attains an equilibrium pressure of

An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressures at temperature $27^{\circ} \mathrm{C}$. The mass of the oxygen withdrawn from the cylinder is nearly equal to:

[Given, $R=\frac{100}{12} \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$, and molecular mass of $\mathrm{O}_2=32,1$ atm pressure $=1.01 \times 10^5 \mathrm{~N} / \mathrm{m}$]

Two gases $A$ and $B$ are filled at the same pressure in separate cylinders with movable pistons of radius $r_A$ and $r_B$, 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 $\frac{r_A}{r_B}$ is equal to

Given below are two statements: One is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$.

Assertion A: Houses made of concrete roofs overlaid with foam keep the room hotter during summer.

Reason R: The layer of foam insulation prohibits heat transfer, as it contains air pockets.

In the light of the above statements, choose the correct answer from the options given below.

The equilibrium state of a thermodynamic system is described by

A. Pressure

B. Total heat

C. Temperature

D. Volume

E. Work done

Choose the most appropriate answer from the options given below.

According to the law of equipartition of energy, the number of vibrational modes of a polyatomic gas of constant $$\gamma=\frac{C_p}{C_v}$$ is ($$C_P$$ where $$C_V$$ are the specific heat capacities of the gas at constant pressure and constant volume, respectively):

A thermodynamic system is taken through the cycle $$abcda$$. The work done by the gas along the path $$b c$$ is:

The following graph represents the $$T$$-$$V$$ curves of an ideal gas (where $$T$$ is the temperature and $$V$$ the volume) at three pressures $$P_1, P_2$$ and $$P_3$$ compared with those of Charles's law represented as dotted lines.

Then the correct relation is :

For the given cycle, the work done during isobaric process is:

A container of volume $$200 \mathrm{~cm}^3$$ contains 0.2 mole of hydrogen gas and 0.3 mole of argon gas. The pressure of the system at temperature $$200 \mathrm{~K}$$ ($$\mathrm{R}=8.3 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$$) will be :-

The temperature of a gas is $$-50^{\circ} \mathrm{C}$$. To what temperature the gas should be heated so that the rms speed is increased by $$3$$ times?

A Carnot engine has an efficiency of $$50 \%$$ when its source is at a temperature $$327^{\circ} \mathrm{C}$$. The temperature of the sink is :-

An ideal gas follows a process described by the equation $$P{V^2} = C$$ from the initial $$({P_1},\,{V_1},\,{T_1})$$ to final $$({P_2},\,{V_2},\,{T_2})$$ thermodynamic states, where C is a constant. Then

Two rods one made of copper and other made of steel of same length and same cross sectional area are joined together. The thermal conductivity of copper and steel are 385 J s^$$-$$1 K^$$-$$1 m^$$-$$1 and 50 J s^$$-$$1 K^$$-$$1 m^$$-$$1 respectively. The free ends of copper and steel are held at 100$$^\circ$$C and 0$$^\circ$$C respectively. The temperature at the junction is, nearly :

Three vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains helium (monoatomic), the second contains fluorine (diatomic) and the third contains sulfur hexafluoride (polyatomic). The correct statement, among the following is :

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

The volume occupied by the molecules contained in 4.5 kg water at STP, if the intermolecular forces vanish away is