Thermodynamics PYQ — Page 5

The total radiant energy per unit area, normal to the direction of incidence, received at a distance $\mathrm{R}$ from the centre of a star of radius $r$, whose outer surface radiates as a black body at a temperature $T \mathrm{~K}$ is given by (where $\sigma$ is Stefan's constant)

The thermo emf $E$ in volt of a certain thermo-couple is found to vary with temperature difference $\theta$ in ${ }^{\circ} \mathrm{C}$ between the two junctions according to the relation $E=30 \theta-\frac{\theta^2}{15}$ The neutral temperature for the thermo-couple will be

If $\mathrm{C}_{\mathrm{p}}$ and $\mathrm{C}_{\mathrm{V}}$ denote the specific heats (per unit mass) of an ideal gas of molecular weight $M$ where $R$ is the molar gas constant.

If $\Delta \mathrm{U}$ and $\Delta \mathrm{W}$ represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat $Q$ in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reservoirs in time $\mathrm{t}$ ?

A monoatomic gas at pressure $p_1$ and $V_1$ is compressed adiabatically to $\frac{1}{8}$ th its original volume. What is the final pressure of the gas?

The internal energy change in a system that has absorbed $2 \mathrm{k}$ cal of heat and done $500 \mathrm{~J}$ of work is :

In thermodynamic processes which of the following statements is not true?

The two ends of a rod of length $L$ and a uniform cross-sectional area $A$ are kept at two temperatures $\mathrm{T}_1$ and $\mathrm{T}_2\left(\mathrm{~T}_1>\mathrm{T}_2\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$, through the rod in a steady state is given by

A black body at $227^{\circ} \mathrm{C}$ radiates heat at the rate of $7 \mathrm{cal} \mathrm{cm}^{-2} \mathrm{~s}^{-1}$. At a temperature of $727^{\circ} \mathrm{C}$, the rate of heat radiated in the same units will be

The two ends of a rod of length $\mathrm{L}$ and a uniform cross-sectional area A are kept at two temperatures $T_1$ and $T_2\left(T_1>T_2\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$, through the rod in a steady state is given by :

The internal energy change in a system that has absorbed $2 \mathrm{kcal}$ of heat and done $500 \mathrm{~J}$ of work is

A black body at $227^{\circ} \mathrm{C}$ radiates heat at the rate of $7 \mathrm{cals} / \mathrm{cm}^2 \mathrm{~s}$. At a temperature of $727^{\circ} \mathrm{C}$, the rate of heat radiated in the same units will be :

In thermodynamic processes which of the following statements is not true?

Оп a new scale of temperature (which is linear) and called the $W$ scale, the freezing and boiling points of water are $39^{\circ} \mathrm{W}$ and $239^{\circ} \mathrm{W}$ respectively. What will be the temperature on the new scale, corresponding to a temperature of $39^{\circ} \mathrm{C}$ on the Celsius scale?

If $Q, E$ and $W$ denote respectively the heat added, change in internal energy and the work done in a closed cycle process, then

An electric kettle takes $4 \mathrm{~A}$ current at $220 \mathrm{~V}$. How much time will it take to boil $1 \mathrm{~kg}$ of water from temperature $20^{\circ} \mathrm{C}$ ? The temperature of boiling water is $100^{\circ} \mathrm{C}$.

At $10^{\circ} \mathrm{C}$ the value of the density of a fixed mass of an ideal gas divided by its pressure is $\mathrm{x}$. At $110^{\circ} \mathrm{C}$ this ratio is

At $10^{\circ} \mathrm{C}$ the value of the density of a fixed mass of an ideal gas divided by its pressure is $x$. At $110^{\circ} \mathrm{C}$ this ratio is

An electric kettle takes $4 \mathrm{~A}$ current at $220 \mathrm{~V}$. How much time will it take to boil $1 \mathrm{~kg}$ of water from temperature $20^{\circ} \mathrm{C}$ ? The temperature of boiling water is $100^{\circ} \mathrm{C}$

If $\mathrm{Q}, \mathrm{E}$ and $\mathrm{W}$ denote respectively the heat added, change in internal energy and the work done in a closed cycle process, then

On a new scale of temperature (which is linear) and called the W scale, the freezing and boiling points of water are $39^{\circ} \mathrm{W}$ and $239^{\circ} \mathrm{W}$ respectively. What will be the temperature on the new scale, corresponding to a temperature of $39^{\circ} \mathrm{C}$ on the Celsius scale?

A black body is at $727^{\circ} \mathrm{C}$. It emits energy at a rate which is proportional to:

If the cold junction of thermocouple is kept at $0^{\circ} \mathrm{C}$ and the hot junction is kept at $T^{\circ} \mathrm{C}$, then the relation between neutral temperature $\left(T_n\right)$ and temperature of inversion $(T)$.