In EM.Ferma, materials and sources are all listed under the "Physical Structure" section of the navigation tree. In other words, there is no separate "Sources" section. For example, you can define default zero-potential perfect electric conductors (PEC) in your project to model metal objects. You can also define fixed-potential PEC objects with a nonzero voltage, which can effectively act as a voltage source for your boundary value problem. In this case, you will solve the Lapalce equation subject to the specified nonzero potential boundary values. Both types of PEC objects are defined from the same PEC node of the navigation tree by assigning different voltage values. Charge and current sources are defined as CAD objects, and you have to draw them in the project workspace just like other material objects.
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=== Using Fixed-Potential PEC Objects as Voltage Sources ===
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[[Image:Static4.png|thumb|330px| EM.Ferma's Wire Current Source dialog.]]
Under the static condition, every point on a PEC object has the same electric potential. By default, this is a zero potential, meaning the PEC object is "grounded". In EM.Ferma, a PEC group has a ''Fixed Potential''' property, which is expressed in Volts and has a zero default value. If you define a new PEC group and keep its default zero voltage, the objects belonging to that group will simply act as metal objects of your physical structure. However, you can define a nonzero voltage value for a PEC group. You can do in the property dialog of the PEC group, which you can access by right-clicking on the group's name in the navigation tree and selecting '''Properties...''' from the contextual menu. In the case of a nonzero voltage, all the PEC objects belonging to that group effectively turn into voltage sources. For example, two parallel PEC plates, one with a zero potential and the other with a nonzero potential represent a simple air-filled capacitor. Note that the voltage value can be positive or negative.
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=== Wire Current Sources ===
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EM.Ferma allows you to define idealized wire current sources. You can use this source type to model filament currents or coils. Wire currents are defined using only line and polyline objects. You also need to define a current value I in Amperes and a wire radius r in the project units. The line or polyline object is then approximated as a volume current with a current density of J = I/(πr<sup>2</sup>) flowing along the line or polyline side's direction. All the wire current sources belonging to the same group have the same color, same current value and same wire radius. The direction of the current can be reversed in wire current sources.
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To add a new wire current source group to a project, right-click on "Wire Currents" on the Navigation Tree, and select "Insert New Current Source..." From the Wire Current Source Dialog, you can change the default brown color of the source group or set the values of the Current and Wire Radius. There is also a check box for "Reverse Current Direction". Note that this will reverse the direction of all the wire currents belonging to the same group. When you draw a line or polyline object under a wire current group in the Navigation Tree, you will notice that direction arrows are placed on the drawn CAD object. You can draw any curve object in the project workspace and convert it to a polyline using [[EM.Cube]]'s Polygonize Tool.
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{{Note| If you draw curve CAD objects under a wire current group, they will be permanently converted to polyline objects before running the simulation engine.}}
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=== Permanent Magnets===
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[[Image:Static6.png|thumb|330px| EM.Ferma's Permanent Magnet Source dialog.]]
A permanent magnet is typically a ferromagnetic material with a fixed inherent magnetization vector. As a result, it can be used as a source in an magnetostatic problem. When a permeable material has a permanent magnetization, the following relationship holds:
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<math> \mathbf{B(r)} = {\mu} (\mathbf{H(r)} + \mathbf{M(r)} ) </math>
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where <b>M(r)</b> is the magnetization vector. In SI units system, the magnetic field <b>H</b> and magnetization <b>M</b> both have the same units of A/m.
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It can be shown that for magnetostatic analysis, the effect of the permanent magnetization can be modeled as an equivalent volume current source:
<math> \mathbf{J_{eq}(r)} = \nabla \times \mathbf{M(r)} </math>
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If the magnetization vector is uniform and constant inside the volume, then its curl is zero everywhere inside the volume except on its boundary surface. In this case, the permanent magnetic can be effectively modeled by an equivalent surface current density on the surface of the permanent magnetic object:
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<math> \mathbf{J_{s,eq}(r)} = \mathbf{M(r)} \times \hat{\mathbf{n}} </math>
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where <math> \hat{\mathbf{n}} </math> is the unit outward normal vector at the surface of the permanent magnet object. Note that the volume of the permanent magnet still acts as a permeable material in the magnetostatic analysis.
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To add a new permanent magnet source group to a project, right-click on "Permanent Magnets" on the Navigation Tree, and select "Insert New Permanent Magnet Source..." From the Permanent Magnet Source Dialog, you can change the default purple color of the source group or set the values of the relative permeability, Magnetization magnitude and unit direction vector components. The default direction vector is z-directed.
== EM.Ferma's Computational Domain ==