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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=== Volume Charge Sources ===
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You can define volume charge sources with a specified charge density in C/m<sup>3</sup> confined to certain region of your project. You use [[EM.Cube]]'s [[Solid Objects|solid objects]] to define volume charge sources. All the charge sources belonging to the same group have the same color and same charge density value. The charge density can be positive or negative.
To add a new charge source group to a project, right-click on "Volume Charges" on the Navigation Tree, and select "Insert New Charge Source..." From the Charge Source Dialog, you can change the default purple color of the source group or set the values of the Charge Density.
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=== Volume Current Sources ===
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You can define volume current sources with a specified current density in A/m<sup>2</sup> confined to certain region of your project. Note that current density is a vectorial quantity and has a magnitude and unit direction vector. You use [[EM.Cube]]'s [[Solid Objects|solid objects]] to define volume current sources. All the volume current sources belonging to the same group have the same color and same current density magnitude and unit vector.
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To add a new volume current source group to a project, right-click on "Volume Currents" on the Navigation Tree, and select "Insert New Current Source..." From the Volume Current Source Dialog, you can change the default brown color of the source group or set the values of the Current Density magnitude and unit direction vector components. The default direction vector is z-directed.
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