Electric Charge...

Two small spheres with masses $$M_1$$ and $$M_2$$ hang on weightless, insulating threads with lengths $$L_1$$ and $$L_2$$. The two spheres carry a charge of $$Q_1$$ and $$Q_2$$ respectively. The spheres hang such that they are level with one another and the threads are inclined to the vertical at angles $$\theta_1$$ and $$\theta_2$$. Which of the following conditions is required if $$\theta_1=\theta_2$$.

Two point charges $$-q$$ and $$+q/2$$ are situated at the origin and the point $$(a,0,0)$$ respectively. The point along the x-axis, where the electric field vanishes is

The smallest electricforce between two changes placed at a distance of 1 m apart is (approximately)

If the coulombian force acting between two protons separated by a distance r is F, what would be the force acting between two $$\alpha-$$particles separated by a distance 2r ?

The black shapes in the figure are closed surfaces. The electric field lines are in red. For which case the net flux through the surfaces is non-zero?

Eight point charges (can be assumed as small spheres uniformly charged and  their centres at the corner of the cube) having values q each are fixed at vertices of a cube .The electric flux through square surface ABCD of the cube is 

Two identical conducting balls A and B have positive charges $$q_1$$ and $$q_2$$ respectively. But $$q_1\neq q_2$$. The balls are brought together so that they touch each other and then kept in their original positions. The force between them is?

Let the electrostatic field E at distance r from a point charge q not be an inverse square but, instead an inverse cubic, e.g., $$\vec{E}=k\frac{q}{r^3}\hat{r}$$. Here k is a constant. Consider the following two statements.
(i) Flux through a spherical surface enclosing the charge is $$\Phi =q_{enclosed}/\epsilon_0$$
(ii) A charge placed inside uniformly charged shell will experience a force.
Choose the correct option.

A certain charge Q is divided into two parts q and $$Q-q$$. How the charge Q and q must be related so that when q and $$(Q-q)$$ is placed at a certain distance apart experience maximum electrostatic repulsion?

A charge $$Q$$ is situated at the centre of a cube. The electric flux through one of the faces of the cube is