Electric charges of $1\,\mu C,\, - 1\,\mu C$ and $2\,\mu C$ are placed in air at the corners $A$, $B$ and $C$ respectively of an equilateral triangle $ABC$ having length of each side $10 \,cm$. The resultant force on the charge at $C$ is......$N$

Consider the charges $q, q$, and $-q$ placed at the vertices of an equilateral triangle, as shown in Figure. What is the force on each charge?

Two particle of equal mass $m$ and charge $q$ are placed at a distance of $16\, cm$. They do not experience any force. The value of $\frac{q}{m}$ is

Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of $30^{\circ}$ with each other. When suspended in a liquid of density $0.8 \;g\, cm ^{-3}$, the angle remains the same. If density of the material of the sphere is $1.6\; g \,cm ^{-3}$, the dielectric constant of the liquid is

A charge $q$ is placed at the centre of the line joining two equal charges $Q$. The system of the three charges will be in equilibrium, if $q$ is equal to

Write Coulomb’s law and explain its scalar form.