Heat Transfer

Two rods of copper and brass ($K_C> K_B$) of same length and area of cross-section are joined as shown. End $A$ is kept a $100°\mathrm{C}$ and end $B$ at $0°\mathrm{C}$ . The temperature at the junction

Find the equivalent conductivity

Three rods $A$, $B$ and $C$ of the same length and same cross-sectional area are joined as shown. Their thermal conductivities are in the ratio $1:2:1.5$. If the open ends of$A$ and $C$ are at $200 °\mathrm{C}$ and $18 °\mathrm{C}$ respectively, the temperature at the junction of $A \& B$ in equilibrium is-

For a black body maintained at temperature, $T_0 \mathrm{K}$ the maximum radiation occurs at wavelength ${\lambda }_0$. If the temperature is raised to$\frac{3}{2}{T}_0 \mathrm{K}$, corresponding wavelength is ${\lambda }_1$. If, ${\lambda }_0-{\lambda }_1=3000 \mathrm{\AA }$ , then value of ${\lambda }_0$, is

Two plates A and B have thermal conductivities $84 \mathrm{W} {\mathrm{m}}^{-1} {\mathrm{K}}^{-1}$ and $126 \mathrm{W} {\mathrm{m}}^{-1} {\mathrm{K}}^{-1}$ respectively. They have same surface area and same thickness. They are placed in contact along their surfaces. If the temperatures of the outer surfaces of  A and B are kept at ${100}^{\circ }\mathrm{C}$ and $0^{\circ }\mathrm{C}$ respectively, then the temperature of the surface of contact in steady state is_____ ${}^{\circ }\mathrm{C}$.

For an object radiating heat at $300 \mathrm{K}$, the wavelength corresponding to maximum intensity is $\lambda$. If the temperature of body is increased by $300 \mathrm{K}$, the new wavelength corresponding to maximum intensity will be

Two spherical objects $A\&B$ are at temperature $T_A$, $T_B$. If $E_A$ and $E_B$ are the power radiated by body $A$and$B$, then value of $\frac{E_A}{E_B}$ will be (given temperatures $T_A=2T_B$, Radius$2R_A = R_B$, $e_A= 0.5e_B$, $e_A$and $e_B$ are the emissivity of $A$ and$B$)

The ratio of emissivities of two bodies is $\frac{e_1}{e_2}=\frac{1}{81}$. Bodies have same surface area and emit total radiant power at the same rate. Find the ratio of wavelengths corresponding to maximum spectral radiance $\frac{{\lambda }_1}{{\lambda }_2}$

There are two parallel infinite black sheets maintained at temperatures $T_{1 }\left(K\right)$ and $T_2$ ($K$). The temperature of a third, identical sheet placed midway and parallel to the sheets at equilibrium will be:

A perfectly black body having area $1{\mathrm{cm}}^2$ is heated to a temperature $1000 \mathrm{K}$. The amount of energy radiated by it in $1 \mathrm{s}$ is (in $\mathrm{J}$)

(Stefan' constant=$5.67\times {10}^{-8} \mathrm{W} {\mathrm{m}}^{-2} {\mathrm{K}}^{-2}$)

When the temperature of a black body increases by $0.1\%$, the wavelength corresponding to maximum emission changes by$0.13 \mathrm{\mu m}$. The initial wavelength corresponding to maximum emission is:

When $150 \mathrm{g}$ of ice at $0°\mathrm{C}$ is mixed with $300 \mathrm{g}$ of water at$50°\mathrm{C}$ in a container, the resulting temperature is

$L_f=3.34\times {10}^5 \mathrm{J} {\mathrm{kg}}^{-1}, {\mathrm{S}}_{\mathrm{w}}=4186 \mathrm{J} {\mathrm{Kg}}^{-1} {\mathrm{K}}^{-1}$

A solid iron sphere and a hollow iron sphere, both have the same mass and are at the same temperature. When placed in a colder surrounding, the heat loss per unit time will be 

A tungsten lamp at a temperature of $3000 \mathrm{K}$ has surface area of $0.3 {\mathrm{cm}}^2$. If the lamp has emissivity of$0.4$, the rate of heat radiated is
 

A metal vessel of negligible heat capacity contains$0.5 \mathrm{kg}$ of water (of specific heat capacity $4200 \mathrm{J} {\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$). It is heated from $15°\mathrm{C}$to $85°\mathrm{C}$ by $750 \mathrm{W}$ immersion heater in$4 \mathrm{minutes}$. The average loss of heat in watts to the surroundings from the vessel during this time is nearly: 

Three identical rods of same metal are connected as shown in figure. In steady state the temperature $T$ is 

Two spheres of radii $r_1$ and $r_2$ have densities ${\rho }_1$ and ${\rho }_2$ and specific heats $C_1$ and $C_2$ respectively. If they are heated to the same temperature, the ratio of their rates of fall of temperature in the same surroundings will be

$n$ moles of a monoatomic gas at temperature $T_1$ is trapped under a piston having area $A$, length $l$, density $\rho$ and thermal conductivity $K$. $P_0$ and $T_0$ are pressure and temperature of the atmosphere. Find length of the gas column as a function of time. Neglect friction and heat loss through the walls of container and sides of piston.

If the absolute temperature of a black body is doubled the percentage increase in the rate of loss of heat by radiation is

Why is the mode of heat transfer in Mercury is by conduction although it is a liquid?