Properties of Electric Lines of Force or Field Lines

1. The electric lines of force are imaginary lines.

2. A unit positive charge placed in the electric field tends to follow a path along the field line if it is free to do      

    so.

3. The electric lines of force emanate from a positive charge and terminate on a negative charge.

4. The tangent to an electric field line at any point gives the direction of the electric field at that point.

5. Two electric lines of force can never cross each other. If they do, then at the point of intersection, there 

    will be two tangents. It means there are two values of the electric field at that point, which is not possible.

    Further, electric field being a vector quantity, there can be only one resultant field at the given point, 

    represented by one tangent at the given point for the given line of force.

6. Electric lines of force are closer (crowded) where the electric field is stronger and the lines spread

    out where the electric field is weaker.

7. Electric lines of force are perpendicular to the surface of a positively or negatively charged body.

8. Electric lines of force contract lengthwise to represent attraction between two unlike charges.

9. Electric lines of force exert lateral (sideways) pressure to represent repulsion between two like charges.

10.The number of lines per unit cross – sectional area perpendicular to the field lines (i.e. density of lines of 

     force) is directly proportional to the magnitude of the intensity of electric field in that region.

11. Electric lines of force do not pass through a conductor. Hence, the interior of the conductor is free from 

     the influence of the electric field.

12. Electric lines of force can pass through an insulator.

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Some of these questions which may be asked in your Board Examination 2012-2013

Q1: what are the characteristic of charges acquired by the objects on rubbing against each other?

Q2: Who suggested first that there are two kinds of charges?

Q3: How can you show that there are two types of charges?

Q4: An ebonite rod is rubbed with the fur or wool. What type of charges do they acquire?

Q5: Is mass of body affected on charging?

Q6: What is the polarity of charge?

Answer these questions in comment box and help your friends