Electric Field Lines (NCERT) - Free MCQ Practice Test with solutions, NEET

Electric field lines are essential for understanding various aspects of electric fields. They illustrate:

• Field strength: The density of lines indicates how strong the electric field is; closer lines mean a stronger field.
• Direction: The arrows on the lines show the direction a positive charge would move within the field.
• Nature of charge: Lines emanate from positive charges and terminate at negative charges, visually representing their nature.

These characteristics together provide a comprehensive view of the electric field's behaviour and effects.

The field lines of a single positive charge are radially outward.

The field lines of single negative charge are radially inward.

For a uniformly charged hollow cylinder, the electric field lines are as shown in figure (b).

In the given figure, the electric lines of force emanate from A and C. Therefore, charges A and C must be positive.

From the given figure it is clear that, maximum number of electric lines of force are associated with charge C, so it must have the largest magnitude.

From the figure, it is clear that, there cannot be a neutral point between a positive and a negative charge. Neutral point can be only there between two like charges i.e„ A and C. As magnitude of charge A is smaller than the magnitude of charge C, therefore, neutral point would lie closer to the charge A.

Electric field strength is maximum where the electric field lines are closer.

Option B is correct.

Key facts: Electrostatic field lines begin on positive charges and end on negative charges (or at infinity), they never cross, they are perpendicular to the surface of a conductor in electrostatic equilibrium, and they do not form closed loops.

The diagram in option B shows field lines meeting the surface of a conductor at angles that are not right angles. If the electric field had a tangential component at the conductor surface, free charges on the conductor would move under that tangential field and the conductor would not be in electrostatic equilibrium. Therefore such a pattern cannot represent a static electrostatic field.

The other diagrams do not violate these basic rules: for example, radial lines from isolated charges or lines meeting conductor surfaces at right angles are allowable patterns. Hence the only impossible diagram is option B.

Final answer: B

In a charge-free region, electric field lines can be taken to be continuous curves without any breaks.