Question
Tue May 03, 2011 By: Nayanika Das Gupta

Why are equipotential surfaces perpendicular to the field lines?

Expert Reply
Tue May 03, 2011
Equipotential surfaces are analogous to different heights of gravitational potential. At different distances
from the Earth, objects have a given amount of potential energy. Just as work must be done against
gravitational force to move an object to a new height, work must be done against an electric force to
move an object to a new equipotential surface. Therefore, it follows that electric field lines must run
perpendicular to equipotential lines just as gravitational field lines run perpendicular to heights of the
same potential energy.
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