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Work (conceptual)

  • Thread starter dimpledur
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I have found that I only need to brush up on my coceptual grasp of work and electrical applications. I have found that I am having negative answers when indeed the answer is positive. My question to you is, if I am following q(Vb-Va)=-W, I am assuming this is the work done by the field, and the work done by an external force (or mover) would be Wmover=-Wfield?
 

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Andrew Mason
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I have found that I only need to brush up on my coceptual grasp of work and electrical applications. I have found that I am having negative answers when indeed the answer is positive. My question to you is, if I am following q(Vb-Va)=-W, I am assuming this is the work done by the field, and the work done by an external force (or mover) would be Wmover=-Wfield?
Whether W is positive or negative depends upon convention for field direction and what you mean by W. The convention is to have the direction of the electric field in the direction which a positive charge will naturally move. You can blame Benjamin Franklin for that.

If one defines the work required to move the charge as W, then W will be positive if the charge is positive and it moves against the direction of the electric field (ie. in the direction of increasing positive potential). If the charge is negative and the charge moves in the direction of the electric field (in the direction of decreasing positive potential which is increasingly negative potential), W also will be positive.

It is opposite (ie. W<0) if the directions of motion are reversed: If the charge is positive, then negative work is required to move the charge in the direction of the electric field (positive work is done to the charge by the field). If the charge is negative and it moves against the direction of the field, W is negative (work done on the charge).

AM
 

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