Forces Between Multiple Charges

The charge on two spheres are $+7 \mu C$ and $-5 \mu C$ respectively. They experience a force $F$. If each of them is given an additional charge of $-2 \mu C,$ then the new force of attraction will be

Three equal charges, each having a magnitude of $2.0\times {10}^{-6}C,$ are placed at the three corners of a right angled triangle of side 3cm, 4cm and 5cm. The force (in magnitude) on the charge at the right angled corner is

Three identical charges each $2\mu C$ lie at the vertices of a right-angled triangle as shown in the figure. Forces on the charge at $B$ due to the charges at $A$ and $C$ respectively are $F_1$ and $F_2$. The angle between their resultant force and $F_2$ .

Two point charges $+3\mathrm{ }\mathrm{\mu }\mathrm{C}$ and $+8\mathrm{ }\mathrm{\mu }\mathrm{C}$ repel each other with a force of $40\mathrm{ }\mathrm{N}$. If a charge of  $–5\mathrm{ }\mathrm{\mu }\mathrm{C}$ is added to each of them, then the force between them will become -

Two equal and opposite charges are placed at a certain distance. The force between them is $F$. If $25\mathrm{\%}$ of one charge is transferred to other, then the force between them is -

A point charge $\text{+}\mathit{\text{Q}}$ is placed at the centroid of an equilateral triangle. When a second charge $\text{+}\mathit{\text{Q}}$ is placed at a vertex of the triangle, the magnitude of the electrostatic force on the central charge is $4\mathrm{ }\mathrm{N}$ . What is the magnitude of the net force on the central charge when a third charge $\text{+}\mathit{\text{Q}}$ is placed at another vertex of the triangle?

If two like charges of magnitude $1{\times 10}^{-9} \mathrm{coulomb}$ and $9\times {10}^{-9} \mathrm{coulomb}$ are separated by a distance of $1 \mathrm{m}$, then the point on the line joining the charges, where the force experienced by a charge placed at that point is zero, is:

The force of interaction between two charges $q_1=6\mu C$ and $q_2=2\mu C$ is 12 N. If charge $q=-2\mu C$ is added to each of the charges, then the new force of interaction is

It is required to hold equal charges $q$ in equilibrium at the corners of a square. What charge when placed at the center of the square will do this?

If a charge $q$ is placed at the centre of the line joining two equal charges $Q$ such that the system is in equilibrium, then the value of $q$ is,