If minimum possible work is done by a refrigerator in converting 100 grams of water at $0^{\circ }\mathrm{C}$  to ice, how much heat (in calories) is released to the surroundings at temperature ${27}^{\circ }\mathrm{C}$ (Latent heat of ice $\left.=80\mathrm{C}\mathrm{a}\mathrm{l}/\mathrm{g}\mathrm{r}\mathrm{a}\mathrm{m}\right)$ to the nearest integer?             

Two moles of helium gas are taken over the cycle ABCDA as shown below in P-T diagram. Assuming the gas to be ideal, the work done on the gas in taking from A to B is

Heat is supplied to an ideal monoatomic gas at constant pressure. The ratio of

An ideal engine whose efficiency is 40%, receives heat at 500 K. If required efficiency is 50%, then intake temperature for the same exhaust temperature is

Choose the correct statement.

Two waves of wavelength 50 cm and 51 cm produced 12 beats per second. The velocity of sound is