Electric Charge...

On doubling the charge on one particle while leaving all other factors the same will:

Two charges $$q_1$$ and $$q_2$$, are separated by a distance r and apply a force F to each other. If both charges are doubled and the distance between them is also doubled, find out the new force between them ? 

Calculate the magnitude of the force between two electrons which are separated by a distance of $$10^{-10}m$$. If the magnitude of the charge is $$10^{-19}C$$ and Coulomb constant is $$10^{10}N\;m^{2}/C^{2}$$.

If the electric force between two unknown charges is attractive, identify which of the following statement must be true?

Find out on which of following factors does strength of the force between charged particles depend.

On doubling the distance between particles while leaving all other factors the same will:

A positive charged particle is kept on the plane surface. There are two points X and Y lies on the plane surface as shown above. If the point Y is three times as far away from Q as point X. What is the ratio of the electric force that would act on a small charge placed at point Y compared to the charge placed at point X?

Electric lines of force about a negative point charge are:

A charge "Q" and "2Q" are 0.05 meters apart and isolated. The ratio of the electrostatic force on the charge Q to the force on charge 2Q is:

Electroscope is used