Do the electric lines of force really exist? What is about the field they represent?

Draw lines of force to represent a uniform electric field. 

Fig. 1.109 shows electric lines of force due to point charges $q_1$ and $q_2$ placed at points $A$ and $B$ respectively. Write the nature of charge on them.

Figure shows two large metal plates, $P_1$ and $P_2$ tightly held against each other and placed between two equal and unlike point charges perpendicular to the line joining them.

What will happen to the plates when they are released?

Figure shows two large metal plates, $P_1$ and $P_2$ tightly held against each other and placed between two equal and unlike point charges perpendicular to the line joining them.

Draw the pattern of the electric field lines for the system.

In the electric field shown in Figure the electric field lines on the left have twice the separation as that between those on the right. If the magnitude of the field at point $A$ is $40 {\mathrm{NC}}^{-1}$, calculate the force experienced by a proton placed at point $A$ Also find the magnitude of electric field at point $B$.