Conductor - Loop

The Loop object is a loop or collection of coaxial loops. The Spec tab of the edit window for a loop is a table of radius, altitude, and winding numbers for the loops. To add a new loop, press the + button. To remove a loop, click on the row of the table for that loop then press the - button. Changes to the table take effect when you press the Apply or Done buttons.

At the bottom of the Spec tab is Wire diameter box where you specify a wire diameter for all loops. Giving the wire a non-zero diameter has two effects. First, the wire is drawn with the specified thickness. Second, the field divergence associated with a filamentary conductor is avoided, since the field is calculated assuming uniform current density within the wire.

As shown in the image above, the radius and altitude parameters may have units, as may the Wire diameter.

This drawing shows a Loop object consisting of two coaxial loops. The first loop has radius r1, altitude z1, and winding N1. The second loop has radius r2, altitude z2, and winding N2.

Calculation details

For non-zero wire diameter BiotSavart uses a formula valid in the limit that the wire diameter is much smaller than the loop diameter.

The field due to the loop is calculated using Complete Elliptic Integrals. However, the loop is drawn using straight segments. The number of segments is set by the nPhi box on the Looks tab. One can also specify a range of angles to draw, but keep in mind that the field is that of a whole loop! Quantities on the Looks tab have no effect upon the calculated field.

Paraxial calculations

A solenoid can use paraxial calculations to improve the speed and accuracy of the calculated magnetic field near the axis.