$A$ point charge $q_1$ exerts a force $F$ upon another point charge $q_2$. If a third charge $q_3$ is placed near the charge $q_2$, then the force that charge $q_1$ exerts on the charge $q_2$ will be

The force between two charges of $+3 \ \mu C$ and $+8 \ \mu C$ is $40 \ N$. If a charge of $-5 \ \mu C$ is added to both,what will be the new force in $N$?

Two charges each equal to $2\,\mu C$ are $0.5\,m$ apart. If both of them exist inside vacuum,then the force between them is.......$N$

Two point charges $q_1$ and $q_2$ are placed at a distance of $50 \ cm$ from each other in air and interact with a certain force. Now,these charges are placed in an oil with a relative permittivity of $5$. If the force between them remains the same,the distance between them in the oil is ........ $cm$.

For the system shown in the figure,find $Q$ such that the resultant force on $q$ is zero.

Two charges placed in air repel each other with a force of $10^{-4} \ N$. When oil is introduced between the charges, the force becomes $2.5 \times 10^{-5} \ N$. The dielectric constant of the oil is: