May be subject to numerical error if field lines are drawn too close to wire where the radius of curvature is large. Enable the user to double click in order to draw a magnetic field line. May be subject to numerical error if field lines are drawn too close to wire where the radius of curvature is large. Show the direction field. Arrows are of unit length.
Color is used to represent magnitude.
The id for the wire or loop. Change the label property of a wire or loop after it has been created. Labels are usually single character identifies. Use the id returned by the add methods to identify the object you wish to change. The id for the wire or loop.