# Equipotentials and electrical field

1. Aug 6, 2009

### nweis

1. The problem statement, all variables and given/known data

Just a quick question. The electrical field is stronger where the voltage is higher right?
Or does it have to do with how close together the equipotential lines are?

Last edited: Aug 6, 2009
2. Aug 6, 2009

### kuruman

If by "voltage" you mean "electrostatic potential difference between two separate points in space", the answer is yes.

The second question should not be an "Or". In a region where equipotentials are closer together over a distance of, say, 1 meter, the electric field is stronger there than in another region where the equipotentials are farther apart over a distance of 1 meter.

After all, the electric field is the rate of change of electrostatic potential with respect to displacement in the direction of maximum change of electric potential.

3. Aug 6, 2009

### JanClaesen

Is the direction of a potential arrow the direction in which a positive particle would move?

4. Aug 6, 2009

### HallsofIvy

Staff Emeritus
"Potential arrow"? The equi-potential lines should have no arrows. They are perpendicular to the field lines. Arrows on a field line point in the direction a positive particle would move.

5. Aug 6, 2009

### Redbelly98

Staff Emeritus
Equipotential lines do not have arrows, but field lines do. The direction of the arrow on an electric field line shows the direction in which a positive particle is accelerated.

6. Aug 7, 2009

### JanClaesen

I'm sorry, it was indeed not a very clever question. Do we measure potential from the negative plate, or does that depend on the context?

Last edited: Aug 7, 2009
7. Aug 7, 2009

### Redbelly98

Staff Emeritus
It will depend on the context. There should be a designated reference point from which potential is measured, which could be the negative plate.

When a HW problem or discussion about capacitors refers to "the voltage" of the capacitor, they mean the potential difference between the positive and negative plates.

Note, getting back to the original question, the electric field inside a capacitor is constant between the two plates. The field is not stronger at the the positive plate.