[Concept] Why is potential 0 when electric field isn't?

[Sean1218]

Say you have a rectangle with -Q charges at top left and bottom left corners, and +Q charges at top right and bottom right corners.

Any point along a horizontal line in the middle will have electric field going to the left, but any point along this line will have a potential of 0. I've been trying to understand this, but having trouble I get that potential is 0 because any point along this line will be equidistant from the two -Q and equidistant from the two +Q.

I think this stems from a lack of understanding of how work and potential (and potential energy) works in an electric field.

 

[Steely Dan]

It is the gradient in potential that determines the electric field. If the potential is zero at some location but non-zero at some nearby location, there will be an electric field as a result of that potential difference. So in general you want to think about the electric field as resulting from differences in potential. This is similar to how a difference in potential generates a force in mechanics. If the potential is uniform everywhere (even if it's non-zero) there is no force.

 

[Daregreatly]

Would you say that it is wrong to say: a presence of charge creates an electric field... And traveling within that electric field, we will see a change in potential as long as we don't just travel perpendicular to the field lines.

 

[ehild]

Would you say that it is wrong to say: a presence of charge creates an electric field... And traveling within that electric field, we will see a change in potential as long as we don't just travel perpendicular to the field lines.

Don't you travel perpendicular to the field lines along the line where the potential is zero?

ehild

 

[Daregreatly]

I don't think there is any reason why we would need to... or a charged particle either. We could force a particle along that line and ask some questions about it though.