Plaster of Paris,when mixed with the correct amount of water,sets into a solid mass due to the formation of:

Two persons of equal height are carrying a long uniform wooden beam of length $l$. They are at distances $\frac{l}{5}$ and $\frac{l}{3}$ from the nearest ends of the rod. The ratio of the normal reaction at their heads is:

Among the following ions,which one has the highest paramagnetism?

In the circuit shown,a meter bridge is in its balanced state. The meter bridge wire has a resistance of $0.1 \ \Omega/cm$. Find the value of the unknown resistance $X$ and the current drawn from the battery of negligible internal resistance.

Along the $X$-axis,three charges $\frac{q}{2}, -q$ and $\frac{q}{2}$ are placed at $x=0, x=a$ and $x=2a$ respectively. The resultant electric potential at $x=a+r$ (if $a \ll r$) is: ($\varepsilon_0$ is the permittivity of free space)

Two spherical soap bubbles of radii $r_1$ and $r_2$ in vacuum combine under isothermal conditions. The resulting bubble has a radius equal to: