Electric field lines are an excellent way of visualizing electric fields. They were first introduced by Michael Faraday himself.
A field line is drawn tangential to the net electric field
at a point. Thus at any point the tangent to the electric field line matches the direction of the electric field at that point. Secondly, the relative density of field lines around a point corresponds to the relative strength (magnitude) of the electric field at that point. In other words if you see more electric field lines in the vicinity of point A as compared to point B, then the electric field is stronger at point A.
Properties Of Electric field lines
Electric field lines always point away from a positive charge and towards a negative point. In fact, electric fields originate at a positive charge and terminate at a negative charge.
Electric field of point charges
Also, field lines never cross each other. If they do, it implies that there are two directions for the electric field at that point. But this is impossible, since electric fields add up vectorially at any point and remember that “A field line is drawn tangential to the net electric field at a point”. Thus, electric field lines can never intersect one another.
As said before field lines are a great way to visualize electric fields. You can almost feel the attraction between unlike charges and the repulsion between like charges as though they are trying to push each other away.
Coming to our initial example of static charge on hair, the direction in which charged hair stands up traces the local electric field lines. The charges on the hair exert forces
on the hair strand as they attempt to leak into the surrounding uncharged space. The hair aligns accordingly so that there is no net force acting on it and inadvertently traces the electric field lines.
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