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Two identical square rods of metal are welded end to end as shown in figure $(i)$ , $20$ calories of heat flows through it in $4$ minutes. If the rods are welded as shown in figure $(ii)$, the same amount of heat will flow through the rods in ....... $\min.$
A body takes $4\, {min}$. to cool from $61^{\circ} {C}$ to $59^{\circ} {C}$. If the temperature of the surroundings is $30^{\circ} {C}$, the time taken by the body to cool from $51^{\circ} {C}$ to $49^{\circ} {C}$ is $....\,min$
The sun radiates electromagnetic energy at the rate of $3.9 \times 10^{26}\,W$. It's radius is $6.96 \times 10^8\,m$. The intensity of sun light at the solar surface will be (in $W/m^2$)
A body cools from a temperature $3T$ to $2T$ in $10$ minutes. The room temperature is $T.$ Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next $10$ minutes will be
The ratio of the diameters of two metallic rods of the same material is $2 : 1$ and their lengths are in the ratio $1 : 4$ . If the temperature difference between their ends are equal, the rate of flow of heat in them will be in the ratio
A solid cylinder of length $L$ and radius $r$ is heat upto same temperature as that of a cube of edge length $a$. If both have same material, volume and allowed to cool under similar conditions, then ratio of amount of radiations radiated will be (Neglect radiation emitted from flat surfaces of the cylinder)
The graph. Shown in the adjacent diagram, represents the variation of temperature $(T)$ of two bodies, $x$ and $y$ having same surface area, with time $(t)$ due to the emission of radiation. Find the correct relation between the emissivity