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MIT Physics 8.02 - Electricity & Magnetism

SECTION : Electrostatics      

SUBJECT: Creating an Electric Field  

An animation of the creation of an electric field by an external agent who separates charges. We start out with five negative electric charges and five positive charges, all at the same point in space. Since there is no net charge, there is no electric field. Now the agent moves one of the positive charges at constant velocity from its initial position to a distance L away along the horizontal axis. After doing that, the agent moves the second positive charge in the same manner to the position where the first positive charge sits. The agent continues on with the rest of the positive charges in the same manner, until all the positive charges are sitting a distance L from their initial position along the horizontal axis. We have color coded the "grass seeds" representation to represent the strength of the electric field. Very strong fields are white, very weak fields are black, and fields of intermediate strength are yellow.

The field lines move in the direction of the energy flow of the electromagnetic field. Over the course of the animation, the strength of the electric field grows as each positive charge is moved into place. That energy flows out from the path along which the charges move, and is being provided by the agent moving the charge against the electric field of the other charges. The work that this agent does to separate the charges against their electric attraction appears as energy in the electric field.





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