Hi,

 

Two surfaces are at 5 mm, the dielectric is an iron piece of 4 mm and 0.5mm of air. I put 100 V at two surfaces (like a capacitor), when the capacitor is charged I cut voltage source. Now, I would like to calculate the fields at surface iron piece and the charge in it. How can I do ?

Iron isn't considered a dielectric. Charges are free to flow, meaning you can probably treat this as two capacitors in series.

Do you have two successive gaps of 0.5mm each? Then they share the 100V equally, so you can deduce the field.

 

For the charge, you need the capacitance, which results from the area and the gap. Air has nearly the same permittivity as void (a few 10^-4 more).

I have try different shapes with femm software and each time when a force move the piece of iron the energy in capacitor go down. Except at the case in the file, it's a circular capacitor and a half cage of iron. When the cage move it give energy and the charge of capacitor go down, so the energy go up. Do you know Femm software and help me to find my error ? I give first file for start position and second file for end position.

Femm files.zip

Edited November 6, 201213 yr by Dsp4