The ends of a metal bar of constant cross-sectional area are maintained at temperatures $T_1$ and $T_2$ which are both higher than the temperature of the surroundings. If the bar is unlagged,which one of the following sketches best represents the variation of temperature with distance along the bar?

What are the modes of heat transfer due to a temperature difference?

Heat loss takes place from a body maintained at a temperature of $400^{\circ} C$ to the surrounding air at $30^{\circ} C$ by convection and to the surrounding surfaces at $30^{\circ} C$ by radiation. The Newton's cooling coefficient is $20 \ W / m^2 \ K$ and the Stefan-Boltzmann constant is $5.67 \times 10^{-8} \ W / m^2 \ K^4$. If the rate of heat loss by convection is equal to the rate of heat loss by radiation, the emissivity of the body surface is

Two rods (one semi-circular and other straight) of the same material and of the same cross-sectional area are joined as shown in the figure. The points $A$ and $B$ are maintained at different temperatures. The ratio of the heat transferred through a cross-section of the semi-circular rod to the heat transferred through a cross-section of the straight rod in a given time is

Differentiate clearly between thermal conduction,thermal convection,and thermal radiation.

Two bodies $A$ and $B$ have thermal emissivities of $0.01$ and $0.81$ respectively. The outer surface areas of the two bodies are the same. The two bodies emit total radiant power at the same rate. The wavelength ${\lambda _B}$ corresponding to maximum spectral radiancy in the radiation from $B$ is shifted from the wavelength corresponding to maximum spectral radiancy in the radiation from $A$ by $1.00\;\mu m$. If the temperature of $A$ is $5802\;K$,then: