Electrostatics Problem--Step-by-Step Description: Step 9

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At last, we can solve the problem and analyze the solution. To do this in one step:

1. On the Problem menu or context menu, click View Field Picture. You will be suggested to solve the problem first, as the results are absent.

2. Click OK.

After finishing, the Postprocessor starts automatically. There are many possibilities to analyze the field in the Postprocessor. We will show only those steps needed to determine the capacitance:

• click icon on the postprocessor toolbar or choose Calculator Window command in the View menu. The calculator window to the left of the picture appears.

• Double click on the Capacitance Wizard item in the calculator window or choose Capacitance Wizard command from View menu. The wizard started. Click the Next button to switch to the next page.

• Select your conductor from the conductor list on the right side of the page. Its potential value appears in the Voltage box. Then click Next.

• Now you can see the list of conductors you have specified given charge to. It contains only one item Strip. Select it by mouse. To employ also an alternative way of capacitance calculating click the Calculate Energy button. The value of stored electrical energy appears in the Energy box. Then click Next.

• The last page of capacitance wizard gives you two values of capacitance calculated by different methods: comparing it you can estimate the calculation precision.

• After the capacitance wizard finishes you can open it again starting from any page by double click on the corresponding item in the calculator window.

Note that, with plane-parallel problems, we specify the sources as specific values per unit depth (e.g., the charge of the strip), and the result is specific capacitance per unit depth, measured in F/m.

Since the mesh is rather rough, the solution gives less accuracy than provided in Elec1_2.pbm.

If you now look through the model provided with Elec1_2.pbm, Elec1.mod, you will find some hints for obtaining a very fine mesh near the vertices E and F - the points of singularity.

Since the Model Editor cannot squeeze the mesh spacing inside the edge, but only from one end to another, two extra vertices have been added in central points of edges AB and EF. The first of these vertices allows the Model Editor to adjust automatically the spacing around it, since the strip is very close to this point. The second vertex is aimed to specify manual spacing value for it, which helps to decrease the total number of nodes in the mesh, without loss of precision.

Done