A rectangular black body of temperature $127^{\circ} \mathrm{C}$ has surface area $4 \mathrm{~cm} \times 2 \mathrm{~cm}$ and rate of radiation is E . If its temperature is increased by $400^{\circ} \mathrm{C}$ and surface area is reduced to half of the initial value then the rate of radiation is

The temperature of an ideal gas is increased from 100 K to 400 K . If ' $x$ ' is the root mean square velocity of its molecules at 100 K , r.m.s. velocity becomes

According to the kinetic theory of gases, when two molecules of a gas collide with each other then

During the isothermal expansion, a confined ideal gas does $(-150) \mathrm{J}$ of work against its surroundings. This means that