What is obtained when calcium carbide reacts with heavy water?

$A$ hollow conducting sphere is placed in an electric field produced by a point charge placed at $P$ as shown in the figure. Let $V_A, V_B$,and $V_C$ be the potentials at points $A, B$,and $C$ respectively. Then:

$A$ $DC$ source with internal resistance $R_0$ is connected to three identical resistors,each of resistance $R$,as shown in the figure. If the thermal power generated in the circuit is highest,then

An infinitely long rod lies along the axis of a concave mirror of focal length $f$. The near end of the rod is at a distance $u > f$ from the mirror. Its image will have a length:

Which of the following has the lowest boiling point?

The thickness of a uniform rectangular metal plate is $5 ~mm$ and the area of each surface is $5 ~cm^2$. In steady state, the temperature difference between the two surfaces of the plate is $14^{\circ} C$. If the heat flowing through the plate in one second from one surface to the other surface is $42 ~J$, then the thermal conductivity of the metal is: