Rules For Drawing Electric Field Lines

A field line is a locus that can be defined using a vector field and a starting location. This starting location can be found within the field. The electric fields are associated with imaginary lines known as electric field lines. The field line begins at the charge and ends either at the charge or at infinity. In this regard, the drawings of these lines are very useful to visualise and representing electric fields around charged objects.  This is because when the field is stronger, the field lines are closer to each other. Also, the number of field lines depends on the charge. The electric field lines always extend from positive charges and the direction is outwards from the charge while for negative charge field lines are directed towards the charge.  In light of this importance, let us look at the three important rules for drawing electric field lines. 

First Drawing Rule 

Many conventions pertain to drawing electric field lines. One of the most important things to keep in mind is that the field line begins at the charge and ends either at the charge or at infinity. The conventions are there to establish one important occurrence: that the electric field lines must communicate the greatest amount of information possible regarding the electric field around a charged object. 

A common convention often used by experts is to cover more charged objects with more electric field lines. So, the objects with greater charge lead to the creation of stronger electric fields. This way, we can understand that when the field is stronger, the field lines are closer to each other. Also, we can understand that the number of field lines depends on the charge.

If a highly charged object is surrounded by more lines, communication of electric field strength can take place effectively in the space surrounding the charged object.

The density of lines that surround any given object reveals the following information:

• Information regarding the quantity of charge on the source charge
• Information regarding the density of lines at a particular location in space 
• Information regarding the electric field strength at that location

One must always keep in mind when following this drawing rule that the field line begins at the charge and ends either at the charge or at infinity.

Second Drawing Rule

A second rule involves drawing the lines of force that are perpendicular to the object’s surfaces. This takes place at the locations where the lines are connected to the surfaces of the object. Just like the first rule, the second rule also relies on the principle that the field line begins at the charge and ends either at the charge or at infinity.

At the surface of objects, there is never an electric force component whose direction is parallel to the surface. This stands for both the following types of objects:

• Symmetrically shaped objects
• Irregularly shaped objects

The direction of the electric force, as well as the electric field, is always perpendicular to the object’s surface.

Third Drawing Rule

The third rule for drawing involves the intersection of lines. In this regard, the following points must be kept in mind:

• The field line begins at the charge and ends either at the charge or at infinity.
• The field lines must never cross.

The point that field lines must never cross is very important when drawing electric field lines. This is because there is a temptation to break this rule for situations that involve a configuration of charges. If electric field lines are permitted to cross each other, then this would throw the whole system into disarray. If this happens, then two distinctly varying values of electric field must be there along their own respective direction. This is never a possibility.  

Conclusion

The electric fields are associated with imaginary lines known as electric field lines. The field line begins at the charge and ends either at the charge or at infinity. Drawing these lines is very important as it helps one to effectively visualise the electric fields. There are three important rules for drawing electric field lines. The first rule involves covering more charged objects with more electric field lines. The second rule involves drawing the lines perpendicular to the surfaces of objects. The third rule pertains to the intersection of lines.