# Field Magnitude and force question

1. Sep 5, 2008

### crh

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

I am needing help with just a conceptual question. I am wondering how the field magnitude varies with the distance between the field lines and if it remains constant along a line of force.

2. Relevant equations

I don't think I use an equation. Maybe Coulomb's equation.

3. The attempt at a solution

I am not for sure how to solve it so I don't know a solution I guess. I think though that the field magnitude is constant if the charges are kept the same. Am I on the right path?

2. Sep 5, 2008

### LowlyPion

Welcome to PF.

The E-field in Coulomb's law is a vector field. I think you should examine the equation to understand how that magnitude calculation is affected by the principle variable r if you are holding q constant. Equipotential lines then refer to the equal magnitudes, but not necessarily the same identical direction at each point along an equipotential. For instance the equipotential lines of a point charge would be spherical concentric shells of equal magnitude in 3 space, with direction determined by the direction to the point charge.

3. Sep 5, 2008

### crh

I guess I am just not understanding. Can you help explain it to me. For one I didn't think that the magnitude changes with distance. I thought it all depended on the amount of charge on a point. This means that if the charges stay the same that it does remain constant along a line of force. Right? Can you explain if I am wrong. Thanks!

4. Sep 5, 2008

### LowlyPion

The magnitude of an electric field will remain the same along an equipotential surface, which for a point charge will be across the surface of a sphere or radius r. For the point charge, the vector direction is guaranteed to be different as it points toward the point charge. (The same as with the electric field having a vector associated with its magnitude.)