[[Image:Back_icon.png|30px]] '''[[EM.Cube#EM.Ferma_Documentation | Back to EM.Ferma Tutorial Gateway]]'''
[[Image:Download2x.png|30px]] '''[http://www.emagtech.com/downloads/ProjectRepo/EMFerma_Lesson2.zip Download projects related to this tutorial lesson]'''
== Getting Started ==
Activate each PEC group by right-clicking on their name in the navigation tree and selecting '''Activate''' from the contextual menu. Then draw two rectangle objects with the location and dimensions given in the table below.
<table>
<tr>
<td>
[[Image:Ferma_L2_Activate.png|thumb|left|480px|Activating PEC group in the navigation tree.]]
</td>
</tr>
</table>
{| class="wikitable"
== Computational Domain, Boundary Conditions & Observables ==
You saw in the previous tutorial lesson that [[EM.Ferma]] automatically places a domain box around your objects. By default, this is a PEC box consisting of six perfect metal plates held at zero potential. In other words, the Dirichlet boundary conditions are applied to your boundary-value problem. The default domain box is placed at a certain offset distance from the largest bounding box enclosing all of your geometric objects in the project workspace. [[EM.Ferma]]'s default domain offset is 20 project units. You can change this offset value individually along the six axial directions. Open the Domain Settings Dialog by clicking the <b>3D Static Domain Settings</b> [[Image:fdtd_domainsettings2.png]] button of Simulate Toolbar or by selecting the menu item <b>Simulate → Computational Domain → Domain Settings…</b> or using the keyboard shortcut {{key|Ctrl+A}}).
In this project, the bottom capacitor plate is held at zero potential, the same as the six domain boundary walls. On the other hand, the top capacitor plate has a potential of 1V. If the domain walls are placed too close to the top plate, strong field lines will establish between them. You need to place the domain walls far enough from the top plate to make them "invisible". Set the six offset values according to the table below:
</table>
You can freeze any geometric Freeze the physical objects to see other objects hidden behind, beneath or inside it. In that case, you will see a wireframe outline of the frozen object and you cannot select it. To freeze an object, right-click on its surface in the project workspace or right-click on its name in the navigation tree and select <b>Freeze</b> from the contextual menu. To unfreeze, repeat the same procedure. In the figure below, the two plates have been shown in freeze state.
<table>
<tr>
<td>
[[Image:Ferma L2 Fig22Ferma_L2_Fig22size.png|thumb|left|480px|Increasing the mesh resolution in the mesh settings dialog.]]
</td>
</tr>
</table>
Run a new electrostatic analysis of the structure with the new field integral observable. At the end of the simulation, open the data manager and select the data file "FI_1_Capacitance.DAT". You can use the {{key|View}} button of the data manager to view the contents of this file in the data manager's built-in spreadsheet. If you do so, you will see a zero value. This is because the value of the capacitance is extremely small. While in the data manager dialog, select "FI_1_Capacitance.DAT" and click the {{key|Notepad}} or {{key|Open}} button. This opens the Windows Notepad, where you will see a value of "1.49196e-011" or 14.92pF.
Using the well-known parallel-plate capacitance formula, you will get:
<tr>
<td>
[[Image:Ferma L2 Fig13.png|thumb|left|480px600px|The new dielectric dialog.]]
</td>
</tr>
<tr>
<td>
[[Image:Ferma L2 Fig15.png|thumb|left|480px600px|The property dialog of the dielectric material group with Mica selected.]]
</td>
</tr>