Final answer:
DA perpendicular to IE signifies that DA could be an equipotential line or surface, which must be perpendicular to the electric field lines (IE). Equipotential lines cannot cross, and when electric field lines are closer together, it indicates a stronger electric field.
Step-by-step explanation:
When DA is said to be perpendicular to IE, in the context of electric fields, one can infer that there are equipotential lines or surfaces represented by DA that are always perpendicular to the electric field lines represented by IE. This is because electric field lines indicate the direction of the electric field, and equipotential lines are always perpendicular to these field lines. Thus, movement along an equipotential line or surface does not require work since there is no component of force in the direction of movement when the force is represented by electric field lines.
The inability of equipotential lines to cross each other stems from the fact that if they did, it would imply two different potentials at the same point in space, which is impossible. Moreover, if electric field lines in a figure are perpendicular to an object, this indicates that the object could be a conductor, since conductors have free charges that move until they are in a state where the electric field inside the conductor is zero, leading to equipotential surfaces forming at the boundary.
Lastly, when electric field lines get closer together, it's indicative of a stronger electric field in that region. Drawing on all of this information can help understand electric fields and potential energy within the field.