Answer:
ield lines point in the direction of the electric field . Field lines cannot cross. If two lines did cross, then the force on a charge would have two directions, which is impossible.
2.
The areal density of field lines (the number of lines per unit area in the plane perpendicular to the field line) is proportional to the magnitude of the electric field . Thus, the larger the field, the higher the density of the field lines, and vice versa.
By definition, rules 1 and 2 hold for any vector field, including the magnetic field.
In addition, for field lines due to electric charges at rest (electrostatics), the following rules apply:
3.
Field lines originate on positive charges and terminate on negative charges, the number of field lines being proportional to the charge. (This prescription is not unique because different people, or the same person under differing circumstances, might choose to use different numbers of field lines for the same charge.)
4.
Field lines do not close on themselves.
Rule 3 is made more precise in Chapter 4 (which eliminates the ambiguity about the number of lines per unit charge). Rule 4 is derived in Chapter 5. These rules are simple, but they are not obvious. They hold only for electric fields due to electric charges at rest. Magnetic field lines do not satisfy rules 3 and 4, but rather have their own set of rules, which we study in Chapter 11.
These rules yield simple pictures only outside of charge distributions. Everywhere within a ball of charge, field lines are originating or terminating. This causes complications that we need not consider here.
Explanation:
