How Do You Calculate the Potential on the Axis of a Uniformly Charged Disk?

[fizzixmaff]

Homework Statement

The potential on the axis of a uniformly charged disk at 4.7 from the disk center is 150 ; the potential 15 from the disk center is 100 .

Homework Equations

I have no idea what the equations are, I read my textbook looking for equations and I've been searching online. I don't have any notes from class because he hasn't covered this.

The Attempt at a Solution

I don't need the solution, just an equation would be beautiful! Thank you in advance :)

 

[ajith.mk91]

I think this equation will work:
(s/2e)(sqrt(z^2+R^2)-z)
where s is surface charge density,e is epsilon,R is the radius of the disk and finally z is the distance along the central axis.

 

[Falcons]

I'm assuming that you're talking about electric potential here, right?
V=-(integral)E(dot)dl
dl is a little portion of the path from point A to point B, so in this case can be re-termed dr. The potential difference (V) from point B to point A is -50, or from A to B is 50. The minus sign from the dot product is already there, so you can ignore that. The limits of your integral depend on what potential difference you're using. If V is from A to B then the limits are from B to A and vice versa. I would use Gauss' law to find E.
Let me know if this helps.

 

[ajith.mk91]

The symmetry of your problem is not sufficient to use Gauss law(Give it a try,The equations will be quite formidable).You can calculate the electrical field either by using cartesian or cylindrical coordinates.Once you get to it you can use del operator to get the potential.

 

[Falcons]

That is true... I guess I misunderstood the description of the problem. Reading the question again, I realize that there isn't a question in the question...
What exactly are we trying to do other than give an equation for potential?