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In this tutorial you will learn about another type of magnetic source called wire current, which is used to model thin current-carrying wires with arbitrary curved shapes. You will use wizards to create solenoids and toroidal coil objects. You will also learn about [[EM.Cube]]'s variables as well as [[Building_Geometrical_Constructions_in_CubeCAD | CubeCAD]]'s versatile curve generator.

A volume current group is characterized by the three components of the current density vector, Jx, Jy and Jz, having units of A/m². You learned about volume current sources in Tutorial Lesson 4. Under a volume current group, you can draw any solid geometric objects such as box, cylinder, cone, <i>etc</i>. A wire current is used to approximate a current filament, that is a current source flowing through a line or curve with a specified finite radius. A wire current group is characterized by its total current (I) having units of Amperes. In [[EM.Ferma]], only line and polyline objects can support wire currents. Under a wire current group, you can define any curve geometric object. However, before running a magnetostatic simulation, the program warns that all the curve object will be polygonized and replaced with polyline objects.

Click on the <b>Solenoid Wizard</b> [[Image:SolenoidWizardIconx.png]] button of the Wizard Toolbar or select the menu item '''Tools &rarr; Component Wizards &rarr; Solenoid'''.

The wizard used [[CubeCAD]]'s '''Curve Generator''' to create a parametric curve to model the solenoid object. In this case, your solenoid is indeed a helix curve. However, the wizard's definition gives a more generalized helical coil object with '''Super-Quadratic''' cross section. Right-click on the name of you your solenoid in the navigation tree and select '''Properties...''' from the contextual menu. This opens up the "Curve Generator" dialog as shown in the figure below:

<td> [[Image:Ferma L5 Fig9.png|thumb|left|640px|Thecurve The curve generator dialog showing the parametric definition of of the solenoid.]] </td>

The definition of the three coordinate functions X(t), y(t) and z(t) also involves variables like "major_rad", "minor_rad", "height", <i>etc</i>. which you saw earlier in the variables dialog. To preserve the parameterization of your solenoid object, you should change its properties from the variables dialog rather than directly from its property dialog.

{{Note|[[CubeCAD]]'s curve generator always creates polyline objects. Unlike ordinary polylines that are characterized by their node sets, the ones created by the curve generator are characterized by mathematical expressions or Python functions.}}

Note that the wizard also define defines two orthogonal, vertical, X- and Y-directed field sensor planes called "FSX" and "FSY", respectively. Change the settings of these observables as follows:

! scope="col"| Cone Length Ratio! scope="col"| Cone Radius Ratio

Run a magnetostatic simulation of your structure and visualize the field sensor plots. You can '''Hide''' any geometric objects to see other objects hidden behind, beneath or inside it. To hide an object, right-click on its surface in the project workspace or right-click on its name in the navigation tree and select '''Hide''' from the contextual menu. To show the object right-click on its surface in the project workspace or right-click on its name in the navigation tree and select '''Show''' from the contextual menu.

Open the data manager and plot the data file "FSX_Z_HTotal.DAT" in EM.Grid as shown in the figure below. As you can see from this figure, the magnetic field along the central axis of the solenoid is almost constant (1191A/m) inside the solenoid in the region 12mm &le; z &le; 36mm.

You may want to start a new blank project for this part of the tutorial lesson. You are going to create the geometry of a toroidal helix coil using one of [[EM.Cube]]'s convenient wizards. To do so, click on the <b>Coil Wizard</b> [[Image:CoilWizardIconx.png]] button of the Wizard Toolbar or select the menu item '''Tools &rarr; Component Wizards &rarr; Toroidal Coil'''.

The geometry of a toroidal helix coil with a circular cross section appears at the center of the project workspace, and its name is added under a new group item called "WIRE_CURRENT" in the navigation tree. The wire current group has the same properties as in the last part.

The geometry of the toroidal helix coil object created by the wizard is fully parameterized. Open '''Variables Dialog''' and review the list of all the variables that have been used for the definition of the toroidal helix object.

| minor_h_radminor_rad_h

| minor_v_radminor_rad_v

Open the property dialog of your coil object and examine the definition of toroidal helix coil in Curve Generator. The parameter "major_rad" determines the major radius of the torus. The cross section of this curve in a generalized super-quadratic curve with two horizontal and vertical radii: "minor_h_radminor_rad_h" and "minor_v_radminor_rad_v". The parameter t varies from zero to 2&pi;. For this project, you reduced the value of the variable "step" to 0.0025 to create a smoother polyline.

<td> [[Image:Ferma L5 Fig24B.png|thumb|left|640px|The properties of the toroidal helix coil shown in CubeCAD's curve generator.]] </td>

! scope="col"| Cone Length Ratio! scope="col"| Cone Radius Ratio

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