The force between two charges $0.06\,m$ apart is $5\,N$. If each charge is moved towards the other by $0.01\,m$,then the force between them will become.........$N$

The distance between charges $5 \times 10^{-11} \, C$ and $-2.7 \times 10^{-11} \, C$ is $0.2 \, m$. The distance at which a third charge should be placed in order that it will not experience any force along the line joining the two charges is . . . . . . $m$.

What is the force (in $N$) between two small charged spheres having charges of $2 \times 10^{-7} \;C$ and $3 \times 10^{-7} \;C$ placed $30 \;cm$ apart in air?

$A$ point charge of $40 \ statC$ is placed $2 \ cm$ in front of an earthed metallic plane plate of large size. The force of attraction on the point charge is.....$dynes$.

In a hydrogen atom,the distance between the electron and proton is $2.5 \times 10^{-11} \ m$. The electrical force of attraction between them will be

Three charges $q$,$Q$,and $4q$ are placed in a straight line of length $l$ at points distant $0$,$\frac{l}{2}$,and $l$ respectively from one end. In order to make the net force on $q$ zero,the charge $Q$ must be equal to