I think you may have left some information out of the question. Can you put more information from your assignment into this question or make a new question on the website? I will assume you are referring to magnetic or electrical field lines. One way to describe these fields exiting an object is via field lines. For instance, you may have seen before diagrams of a magnet with a large number of curved lines coming out and going back into the poles of the magnet. These are field lines, and scientists draw these invisible lines to help describe magnets and their behavior. When the field lines are close together, there is a stronger magnetic field. The field lines are the paths of a pretend charge particle and where it will move when placed in that spot. When you move a wiire through the field lines so it "cuts" through them, you get an electric current. This is how generators work. Field lines are also used for electrical field description and even perhaps gravitational field description. Another way to draw something descriptive about the field is equipotential lines, which are drawn perpendicular to the field lines and describe how much energy a charged particle has depending on where it is relative to the magnet.
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