Electric Charge...

Two possitively charged spheres of masses $$m_1$$, and $$m_2$$, are suspended from a common point at the ceiling by identical insulating mass-less strings of length I. Charges on the two spheres are $$q_1$$ and $$q_2$$, respectively. At equilibrium both strings make the same angle $$\theta$$ with the vertical. Then :

The charges 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 :

Distance between the two point charges in increased by $$20$$%. Force of interaction between the charges.

Two sphere of electric charges $$+2$$ nC and $$-8$$ nC are placed at a distance '$$d$$' apart. If they are allowed to touch each other, what is the new distance between them to get a repulsive force of same magnitude as before?

A girl brings a positively charged rod near a thin neutral stream of water flowing from a tap. She observes, that the water stream, bends towards her. Instead, if she is to bring a negativity charged rod near to the stream, it will :

A charge of $$0.8$$ coulomb is divided into two charges $${Q}_{1}$$ and $${Q}_{2}$$. These are kept at a separation of $$30cm$$. The force on $${Q}_{1}$$ is maximum when :

Two copper balls each weighing 10 g are kept in air 10 cm apart. If one electron from every $$\displaystyle { 10 }^{ 6 }$$ atoms is transferred from one ball to the other, the coulomb force between them is (atomic weight of copper is 63.5) :

The force between two point charges placed in a material medium of dielectric constant $$\varepsilon_r$$ is $$F$$. If the material is removed, then the force between them becomes:

Two spherical conductors A and B having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor C having same radius as that of A but uncharged is bought in contact with B and then with A. then new force of repulsion between B and A will be :

If electrical force between two charges is $$200 N$$ and we increase $$10$$% charge on one of the charges and decrease $$10$$% charge on the other, then electrical force between them for the same distance becomes :