Electric Field Lines

Electric field lines are a representation used to visualize the electric field surrounding charged objects.

• They provide a way to understand the direction and strength of the electric field at different points in space.
• It helps analyze electric fields in various situations, such as around point charges, between parallel plates, or within complex arrangements of charges.
• The tangent drawn at any point on the electric field lines shows the direction of the electric field at that particular point.

Direction of Electric Field Lines

The concept of an electric field line is used to define an electric field near charged particles. They were first used by Michael Faraday to define an electric field due to an electron and a proton. They are also called electric lines of force.

They are regular lines without any breaks and are curved in nature. In the case of a positive charge, the direction of the electric field lines is radially outwards, and in the case of a negative charge, the direction of the electric field lines is radially inwards. Also, the density of the electric field lines shows the strength of the electric field, i.e., the more electric field lines in an area, the stronger the electric field there.

Properties

• Electric field lines never intersect each other.
• Electric field lines are always perpendicular to the surface of the charge.
• For a single charge, the field lines go from the surface of the charge to infinity.
• The magnitude of the electric field and the number of field lines are proportional to each other.
• In a uniform electric field, field lines are evenly spaced and parallel to each other.
• In a non-uniform electric field, the field lines are closer together where the field is stronger and farther apart where it is weaker.
• Electric field lines originate from positive charges and terminate on negative charges.

Rules for Drawing Electric Field Lines

The rules used for drawing electric field lines are discussed below:

• For a positive charge, electric field lines always start at its surface and go up to infinity; for a negative charge, they start from infinity and end at its surface.
• The more field lines in an area, the stronger the electric field.
• Electric field lines never intersect each other.
• Electric field and electric field lines are always tangent at the point where they pass through.

Electric Field Lines for Different Charges

Using the above rules, we can draw electric field lines for different configurations of electric charges.

Electric Field Lines for Individual Charges

In the case of an individual positive charge, the direction of the electric field line is radially outwards, and in the case of an individual negative charge, the direction of the electric field line is radially inwards.

Electric Field Lines for Two Equal and Unlike Charges

For two equal and unlike charges, the electric field will originate from the positive charge and enter into the negative charge, forming a closed loop.

Electric Field Lines for Two Equal and Like Charges

In the case of two equal and like charges, both will exert a repulsive force on each other, and the arrangement of electric field lines will be on either side of each charge.

Solved Problems

Example 1: At any time, a force of 10 N is operating on the charge of 18 μC. Determine the intensity of the electric field at that location.

Solution: Given: 
F = 10 N, q = 18 μC

E = F/q
E = 10 / 18 × 10^-6
E = 5.5 × 10⁵ N/C

Example 2: Calculate the strength of the electric field at a distance of 12 cm with a voltage of 68 V.

Solution: Given:
V = 68 V, r = 12 cm

E = V/r

E = 68/12
E = 5.66 V/cm

Example 3: A force of 12 N is acting on the charge of 27 μC. Find Electric Field.

Solution: Given: 
F = 12 N, q = 27 μC

E = F/q

E = 12 / 27 × 10^-6
E= 4.44 × 10⁵ N/C

Example 4: If The electric field is 6.4 N/C at a distance of 6 cm, then find the voltage.

Solution: Given: 
E = 6.4 N/C, r = 6 cm

V = E × r

V = 6.4 × 6
V = 38.4 V

Related Articles:

• Electric Potential Energy
• Electric Field due to a Point Charge 
• Electric Current