Thermodynamics PYQ — Page 20

If $\mathrm{C}_p$ and $\mathrm{C}_{\mathrm{v}}$ denote the specific heats of nitrogen per unit mass at constant pressure and constant volume respectively, then

One end of a thermally insulated rod is kept at a temperature $T_1$ and the other at $T_2$. The rod is composed of two sections of lengths $\ell_1$ and $\ell_2$ and thermal conductivities $k_1$ and $k_2$ respectively. The temperature at the interface of the two sections is 

When a system is taken from state $i$ to state $f$ along the path $\mathrm{iaf}$, it is found that $Q=50 \mathrm{~cal}$ and $\mathrm{W}=20 \mathrm{~cal}$. Along the path' $\mathrm{ibf}$ $\mathrm{Q=36 ~cal}$. $\mathrm{W}$ along the path $\mathrm{ibf}$ is 

The work of $146 \mathrm{~kJ}$ is performed in order to compress one kilo mole of gas adiabatically and in this process the temperature of the gas increases by $7^{\circ} \mathrm{C}$. The gas is $\left(\mathrm{R}=8.3 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right)$

Assuming the sun to be a spherical body of radius $\mathrm{R}$ at a temperature of $\mathrm{T} \mathrm{K}$, evaluate the total radiant power, incident on Earth, at a distance $r$ from the Sun.

Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature $T_0$, while Box $B$ contains one mole of helium at temperature $(7 / 3) T_0$. The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature. (Ignore the heat capacity of boxes). Then, the final temperature of the gases, $T_f$, in terms of $T_0$ is

The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$ respectively. The radial rate of flow of heat in a substance between the two concentric sphere is proportional to 

The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is 

A gaseous mixture consists of $16 \mathrm{~g}$ of helium and $16 \mathrm{~g}$ of oxygen. The ratio $\frac{C_p}{C_v}$ of the mixture is

A system goes from $A$ to $B$ via two processes I and II as shown in the figure. If $\Delta \mathrm{U}_1$ and $\Delta \mathrm{U}_2$ are the changes in internal energies in the processes I and II respectively, the 

Which of the following is incorrect regarding the first law of thermodynamics?

If the temperature of the sun were to increase from $T$ to $2 T$ and its radius from $R$ to $2 R$, then the ratio of the radiant energy received on earth to what it was previously will be

Which of the following statements is correct for any thermodynamic system?

One mole of ideal monoatomic gas $(\gamma=5 / 30)$ is mixed with one mole of diatomic gas $(\gamma=7 / 5)$. What is $\gamma$ for the mixture? $\gamma$ denotes the ratio of specific heat at constant pressure, to that at constant volume.

The thermistors are usually made of

The thermo emf of a thermocouple varies with the temperature $\theta$ of the hot junction as $\mathrm{E}=\mathrm{a} \theta+\mathrm{b} \theta^2$ in volts where the ratio $\mathrm{a} / \mathrm{b}$ is $700^{\circ} \mathrm{C}$. If the cold junction is kept at $0^{\circ} \mathrm{C}$, then the neutral temperature is

Time taken by a $836 \mathrm{~W}$ heater to heat one litre of water from $10^{\circ} \mathrm{C}$ to $40^{\circ} \mathrm{C}$ is

Two thermally insulated vessels 1 and 2 are filled with air at temperatures $\left(T_1, T_2\right)$, volume $\left(V_1, V_2\right)$ and pressure $\left(P_1, P_2\right)$ respectively. If the valve joining two vessels is opened, the temperature inside the vessel at equilibrium will be

The temperature of two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity $K$ and $2 K$ and thickness $x$ and $4 x$, respectively are $T_2$ and $T_1\left(T_2>T_1\right)$. The rate of heat transfer through the slab, in a steady state is $\left(\frac{A\left(T_2-T_1\right) K}{x}\right) f$, with $f$ equal to 

The earth radiates in the infra-red region of the spectrum. The spectrum is correctly 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 $\mathrm{C}_{\mathrm{p}} / \mathrm{C}_{\mathrm{v}}$ for the gas is

Which of the following parameters does not characterize the thermodynamic state of matter?

In the nuclear fusion reaction ${ }_1^2 \mathrm{H}+{ }_1^3 \mathrm{H} \rightarrow{ }_2^4 \mathrm{He}+\mathrm{n}$ given that the repulsive potential energy between the two nuclei is $\sim 7.7 \times 10^{-14} \mathrm{~J}$, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann's Constant $\mathrm{k}=1.38 \times 10^{-23} \mathrm{~J} / \mathrm{K}$ ]

"Heat cannot by itself flow from a body at lower temperature to a body at higher temperature" is a statement or consequence of