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Swapnil Das, Samara Simha Reddy, and Sravanth C. contributed

Field line is a locus that is defined by a vector field and a starting location within the field. For the electric fields, we have electric field lines. As we have seen in Electrostatics, electric charges create an electric field in the space sorrounding them. It acts as a kind of "map" that gives that gives the direction and indicates the strength of the electric field at various regions in space. The concept of electric field lines was introduced by Michael Faraday, which helped him to easily visualize the electric field using intuition rather than mathematical analysis.

Contents

• Definition of Electric Field Lines
• Properties of Electric Field Lines

An electric field line is an imaginary line or curve drawn through a region of empty space so that its tangent at any point is in the direction of the electric field vector at that point. The relative closeness of the lines at some place gives an idea about the intensity of electric field at that point.

Electric field lines have some important and interesting properties, let us study them.

• Electric field lines always begin on a positive charge and end on a negative charge, so they do not form closed curves. They do not start or stop in midspace
• The number of electric field lines leaving a positive charge or entering a negative charge is proportional to the magnitude of the charge.
• Electric field lines never intersect.
• In an uniform electric field, the field lines are straight, parallel and uniformly spaced.
• The electric field lines can never form closed loops, as line can never start and end on the same charge.
• These field lines always flow from higher potential to lower potential.
• If the electric field in a given region of space is zero, electric field lines do not exist.
• The tangent to a line at any point gives the direction of the electric field at the point. Also, this is the path on which a positive test charge will tend to move if free to do so.

Why don't electric field lines intersect \(?\)

If the electric field lines intersect, then two tangents could be drawn at their point of intersection. Thus, the electric field intensity at the point will have two directions, which is absurd.

a) only a) and c) a) and b) b) only Reveal the answer

The above diagram shows the lines of electric force and equipotential lines on a particular plane. Which of the following statements is correct?

a) The electric potential at point A is higher than that at point B. b) The electric field strength at point A is the same as that at point B. c) The work done by the electric force when an electrically charged particle is moved from point B to C along the equipotential line is zero.

The correct answer is: a) and c)

\(a)\) Since the direction of the electric force line is the direction away from the point P , there must be a positive charge at point P. Hence, the electric potential at point A is higher than that at point B.

\(b)\) Recall that electric field strength is proportional to the number of electric force lines per unit area. Then the electric field strength at point A is stronger than that at point B.

\(c)\) When an electrically charged particle is moved along the equipotential line, the direction of the electric force line is perpendicular to the direction of the moving path. Hence, the work done by the electric force when an electrically charged particle is moved from point B to C along the equipotential line is zero.

Why aren't there any electric field lines inside a conductor \( ?\)

That is because of the fact that electric field inside a conductor is zero \( !\)

When is an electric field said to be uniform \(?\)

An electric field is said to be uniform, when it has the same magnitude and direction in a given region of space.

Both A and B have the same sign. If we put a positive charge at P, it will be dragged towards B. The electric field strength at point P is stronger than that at point Q. The quantity of the electric charge A is larger than that of B. Reveal the answer

The above diagram shows electric field lines generated by two point charges A and B. Which of the following explanations is NOT correct?

The correct answer is: If we put a positive charge at P, it will be dragged towards B.

\(1)\) Since the electric field lines are emanating from the two point charges A and B, both of them must be positive charges.

\(2)\) The number of electric field lines emanating from A is greater than that from B. Hence, the quantity of the electric charge A is larger than that of the electric charge B.

\(3)\) Recall that electric field strength is proportional to the density of the electric field lines. Then, since the density of the electric field lines at point P is greater than that at point Q, the electric field strength at point P is stronger than that at point Q.

\(4)\) If we put a positive charge at point P, then it will move along the electric field lines. Thus, it will not be dragged towards B. Furthermore, since B is a positive charged point charge, any positive charge can't dragged towards B.

See also

• Electric Potential

• Charge and Electric Fields

• Electric Flux

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