Here, q = 30 °, E = 2 x 10⁵ N C^–1 , τ= 4 N m,
l = 2 cm = 0.02 m, q = ?
τ= pE sinq = (ql)E sinq

Here, r = 10 cm, q = 3.2 x 10^–7 C

It is not possible to remove or add protons/neutrons to an atom, but electrons can be added or removed by an atom easily.
By adding electrons it becomes negatively charged.
By removing electrons it becomes positively charged. 

Let φ_A , φ_B and φ_C are the electric flux linked with surface is A, B and C.
According to Gauss theorem,

As at a corner, 8 cubes can be placed symmetrically, flux linked with each cube (due to a charge Q at the corner)
will be  

Now for the faces passing through the edge A, electric field E at a face will be parallel to area of face and so flux for these three faces will be zero. Now as the cube has six faces and flux linked with three faces (through A) is zero, so flux linked with remaining three faces will be  
Hence, electric flux passed through all the six faces of the cube is  

The  electrostatic force  is an attractive and repulsive  force  between particles are caused due to their electric charges. The electric  force  between stationary charged bodies is conventionally known as the  electrostatic force. 

Electric flux emerging from the cube does not depend on size of cube.

In a uniformly charged hollow conducting sphere

Conductors are materials that permit electrons to flow freely from particle to particle. An object made of a conducting material will permit a charge to be transferred across the entire surface of the object.

Electric field inside the charged spherical shell is zero as there is no charge inside it.