# Homework Help: Where does a field line meet the surface of the conductor?

1. Oct 11, 2008

### FourierX

1. The problem statement, all variables and given/known data
In the field of a point charge over a plane, if you follow a field line that starts at the point charge in a horizontal direction, that is, parallel to the plane, where does it meet the surface of the conductor?

2. Relevant equations
The problem 'hint' is "You'll need Gauss' law and a simple integration."

3. The attempt at a solution
The electric field on the surface of the conductor at a radius R=$$\sqrt{r^{2}+h^{2}}$$ (h is the height of the pt charge, r is the x component of the radius on the plane), the Electric field due to the point charge is:
E=$$\frac{-2Qh}{(r^{2}+h^{2})^{3/2}}$$. This is given in the book.
I have no idea where to start...

Last edited: Oct 11, 2008
2. Oct 12, 2008

### Gokul43201

Staff Emeritus
Have you quoted the question exactly as it was given to you? It appears somewhat poorly written. Is this supposed to be understood in the context of a previous problem, for instance?

Specifically, is the point charge located near an infinite, grounded conducting plane?

Please write down the original question exactly as provided.

3. Oct 13, 2008

### FourierX

the plane is grounded and i figured out that the net electric field is directed towards negative Z direction. I have to find out the distance of a point in the plane (x-axis). I thought of using a concept of projectile motion as the trajectory looks parabolic, but I am not quite sure how to get to the final conclusion.