Exercises

Two identical objects $\mathrm{A}$ and $\mathrm{B}$ are at temperatures $T_{\mathrm{A}}$ and $T_{\mathrm{B}}$  respectively. Both objects are placed in a room with perfectly absorbing walls maintained at a temperature $T(T_{\mathrm{A}}>T>T_{\mathrm{B}})$. The objects $\mathrm{A}$ and $\mathrm{B}$ attain the temperature $T$ eventually. Select the correct statements from the following

Which of the following graph shows the correct variation in intensity of heat radiations by black body and frequency at a fixed temperature:

Radius of a conductor increases uniformly from left end to right end as shown in figure. Material of the conductor is isotropic and its curved surface is thermally isolated from surrounding. Its ends are maintained at temperatures $T_1$ and $T_2\left( T_1>T_2\right)$

If, in steady state, heat flow rate is equal to $H,$ then which of the following graphs is correct -

A body cools in a surrounding which is at a constant temperature of ${\theta }_0$. Assume that it obeys Newton's law of cooling. Its temperature $\theta$ is plotted against time $t$. Tangents are drawn to the curve at the points $P\left(\theta ={\theta }_2\right)$ and $Q\left(\theta ={\theta }_1\right)$. These tangents meet the time axis at angles of ${\varphi }_2$ and ${\varphi }_1$, as shown.

A metal rod of length 2m has cross sectional areas 2A and A as shown in figure. The ends are maintained at temperatures 100°C and 70°C. The temperature at middle point C is

The total energy radiated from a black body source is collected for one minute and is used to heat a quantity of water. The temperature of the water is found to increase from $20°\mathrm{C}$ to $20.5°\mathrm{C}$. If the absolute temperature of the black body is doubled and the experiment is repeated with the same quantity of water at $20°\mathrm{C}$, then the temperature of water will be

A liquid cools down from $70°\mathrm{C}$ to $60°\mathrm{C}$ in $5$ minutes. The time taken to cool it from $60°\mathrm{C}$ to $50°\mathrm{C}$ will be

If a metallic sphere gets cooled from $62°\mathrm{C}$ to $50°\mathrm{C}$ in $10$ minutes and in the next $10$ minutes gets cooled to $42°\mathrm{C}$, then the temperature of the surroundings is