Parallel Plate Capacitor Diameter

[tomizzo]

Homework Statement

Two circular disks spaced 0.50 mm apart form a parallel-plate capacitor. Transferring 1.70 ×109 electrons from one disk to the other causes the electric field strength to be 3.50 ×105N/C.

What are the diameters of the disks?

Homework Equations

Refer to attachment

The Attempt at a Solution

So I substitute everything into the formula and end up getting R = .5 mm. I then double this to find the diameter and still get the wrong answer. Any ideas?

 

[gneill]

Homework Statement

Two circular disks spaced 0.50 mm apart form a parallel-plate capacitor. Transferring 1.70 ×109 electrons from one disk to the other causes the electric field strength to be 3.50 ×105N/C.

What are the diameters of the disks?

Homework Equations

Refer to attachment

The Attempt at a Solution

So I substitute everything into the formula and end up getting R = .5 mm. I then double this to find the diameter and still get the wrong answer. Any ideas?

Not sure what you're intending to do with that equation you attached. It looks like the on-axis field for a charged circular disk at some distance z from the disk along the axis. But here you have a parallel plate capacitor and the field will be (essentially) uniform between the parallel plates.

Look instead to formulas related to parallel plate capacitors.

 

[lightgrav]

convert Q to Coulombs, then use Gauss to obtain Area.