The height of a waterfall is $50 \ m$. If $g = 9.8 \ m/s^2$, the difference between the temperature at the top and the bottom of the waterfall is: (in $^{\circ} C$)

On which of the following four processes does the functioning of a bimetallic strip depend?
$(i)$ Radiation
$(ii)$ Energy conversion
$(iii)$ Melting
$(iv)$ Thermal expansion

$A$ student takes $50 \, g$ of wax (specific heat $= 0.6 \, cal/g \cdot ^\circ C$) and heats it until it boils. The graph between temperature and time is shown below. The heat supplied to the wax per minute and the boiling point are respectively:

$A$ refrigerator converts $500\,g$ of water at $25\,^{\circ}C$ into ice at $-10\,^{\circ}C$ in $3\,hours\,40\,minutes$. The quantity of heat removed per minute is ........ $cal/\min$.
(Specific heat of water $= 1\,cal/g\,^{\circ}C$,Specific heat of ice $= 0.5\,cal/g\,^{\circ}C$,Latent heat of fusion $= 80\,cal/g$)

The top of a lake gets frozen at a place where the surrounding air is at a temperature of $-20\,^oC$. Then

The point on the pressure-temperature phase diagram where all three phases (solid,liquid,and gas) co-exist is called: