Two point charges $q_2 = 3 \times 10^{-6} \ C$ and $q_1 = 5 \times 10^{-6} \ C$ are located at $B(3, 5, 1) \ m$ and $A(1, 3, 2) \ m$ respectively. Find the magnitude of the force on $q_1$ due to $q_2$.

In the figure,the force on the charge at $A$ in the direction perpendicular to $BC$ is ...... .

An infinite number of point charges,each carrying $1 \,\mu C$ charge,are placed along the y-axis at $y=1 \,m, 2 \,m, 4 \,m, 8 \,m, \ldots$. The total force on a $1 \,C$ point charge,placed at the origin,is $x \times 10^{3} \,N$. The value of $x$,to the nearest integer,is .........
[Take $\frac{1}{4 \pi \epsilon_{0}}=9 \times 10^{9} \,N m^{2}/C^{2}$]

$A$ 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.....$dynes$.

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

For the regular pentagon system shown in the figure,find the net electrostatic force on the charge $q_0$ placed at the center.