Question

A long cylindrical shell carries positive surface charge $\sigma$ in the upper half and negative surface charge $−\sigma$ in the lower half. The electric field lines around the cylinder will look like figure given in :
(figures are schematic and not drawn to scale)
A.
B.
C.
D.

Answer 1

The electric field line is an imaginary curve or line throughout the space around a charged body. So, that tangent at any point on the curve of the electric field vector gives the direction of the electric field at that point.

Complete answer:
Electric field lines follow some important characteristics:-
• The field lines start from positive charges and terminate at negative charges. If there is a single charge, they may start or end at infinity.
• Electric field lines never form any closed loops. This follows from the conservation of the electric field.
• In a charge free region, electric field lines can be taken to be continuous curves without breaking its homogeneity in space.
• Electric field lines can never cross each other because at the point of intersection two tangents can be drawn that will show two different directions of the electric field at the same point which is absurd.

Now let's observe the diagrams given in options:

The schematic figure of option (A) clearly shows that the both surface charges are not separated, so the entire body will be completely neutralized (having zero surface charge).
The schematic figure of option (B) is not fulfilling the necessary property of electric field that Electric field lines never form any closed loops.
The schematic figure of option (D) is not fulfilling the necessary property of electric field that In a charge free region, electric field lines can be taken to be continuous curves without breaking its homogeneity in space.

Hence, the correct answer is option (C).

Note: In order to solve such concept-based theoretical questions students should have proper knowledge of properties regarding the electric field to avoid the mistakes while solving such theoretical questions one must have to read the chapter carefully and grasp the basic physics behind the concepts. One should also practice multiple selective problems on this topic for better understanding.