Thermal Properties of Matter

A black body is at a temperature of $\text{5760}\text{K.}$ The energy of radiation emitted by the body at wavelength $\text{250}\text{nm}$ is $U_{1}$, at wavelength $\text{500}\text{nm}$ is $U_{2}$ and that at…

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are $K_{1}$ and $K_{2}$. The thermal conductivity of the composite rod will be

The power radiated by a black body is P and it radiates maximum energy at wavelength, $\lambda\,_{0}$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength…

The quantities of heat required to raise the temperature of two solid copper spheres of radii $r_{1}$ and $r_{2}\left(r_{1}=1.5r_{2}\right)$ through $1K$ are in the ratio:

A spherical black body with a radius of $12\mathrm{cm}$ radiates $450W$ power at $500K$. If the radius were halved and the temperature doubled, the power radiated in watt would be

Assertion : The conductivity of an electrolyte is very low as compared to a metal at room temperature. Reason : The number density of free ions in electrolyte is much smaller as compared to number density of free…

A cup of coffee cools from 90$^\circ$C to 80$^\circ$C in t min, when the room temperature is 20$^\circ$C. The time taken by a similar cup of coffee to cool from 80$^\circ$C to 60$^\circ$C at a room temperature same at…

Three stars A, B, C have surface temperatures TA, TB,TC respectively. Star A appears bluish, star B appears reddish and star C yellowish. Hence,

A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is: (Latent…

A copper rod of 88 cm and an aluminum rod of unknown length have their increase in length independent of increase in temperature. The length of aluminum rod is $\alpha$Cu=1.7$\times$10-5 K-1 and…

Steam at 100 oC is passed into 20 g of water at 10 oC. When water acquires a temperature of 80oC, the mass of water present will be:[Take specific heat of water =1 cal g-1 oC-1 and latent heat of steam =540 cal g-1]

Coefficient of linear expansion of brass and steel rods are \$\alpha_{1}$ and \$\alpha_{2}$. Lengths of brass and steel rods are \$l_{1}$ and \$l_{2}$, respectively. If \$(l_{2}-l_{1})$ is maintained the same at all…