Four rods of same material with different radii $r$ and length $l$ are used to connect two reservoirs of heat at different temperatures. Which one will conduct most heat ?

A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers $140°F$. What is the fall in temperature as registered by the Centigrade thermometer …… $^o$

Two substances $A$ and $B$ of equal mass $m$ are heated at uniform rate of $6\,cal\,s^{-1}$ under similar conditions. A graph between temperature and time is shown in figure. Ratio of heat absorbed $H_A/H_B$ by them for complete fusion is

$50\,g$ of copper is heated to increase is temperature by $10\,^oC$. If the same quantity of heat is given to $10\,g$ of water, the rise in its temperature is  …….. $^oC$ (Specific heat of copper $= 420\,J-kg^{-1}\,^oC^{-1}$ )

Steam at $100\,^oC$ is passed into $22\,g$ of water at $20\,^oC$. The mass of water that will be present when the water acquires a temperature of $90\,^oC$ (Latent heat of steam is $540\, cal/g$ ) is ………… $\mathrm{g}$