# Homework Help: [Concept] Why is potential 0 when electric field isn't?

1. Apr 17, 2012

### 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.

2. Apr 18, 2012

### 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.

3. May 31, 2012

### 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.

4. May 31, 2012

### ehild

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

ehild

5. May 31, 2012

### 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.

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