has a wonderful copy of your applet
the internal coding has been redone to suit the new Ejs 3D objects.
i was having a hard time figuring out how to change the older objects into the newer ones especially the data field was b which was a 4 dimensional variable  while the newer Ejs objects didn't have 'data' field.
They also have good description which is in a html page
[table][tr][td][table][tr][td]Magnetic Field from Loops
The EJSMagnetic Field from Loops model computes the B-field created by an electric current through a straight wire, a closed loop, and a solenoid. The user can adjust the vertical position of the slice through the 3D field.
1. Watch the simulation as the field changes from the field around a long straight current-carrying wire to the field near a coil. Explain what happens to the field. Inside a coil of many loops, why is the field fairly uniform near the center (think about vector addition and what vectors would be adding together near the center).
2. There is an arrow on each end of the wire (red and blue). Which one shows the direction of the current in the wire? Explain.
3. The simulation also shows the magnetic flux. What is flux? Therefore, what do the different colors represent and why (i.e is pink higher flux than yellow or vice versa)? and what does "higher flux" mean in terms of the geometry and field strength?)?
The Magnetic Field from Loops simulation was created by Fu-Kwun Hwang using the Easy Java Simulations (EJS) modeling tool and was adapted to EJS version 4.1 by Robert Mohr and Wolfgang Christian at Davidson College. Additional exercises written by Anne J. Cox. You can examine and modify the model for this simulation if you have Ejs installed by right-clicking within the simulation frame and selecting "Open Ejs Model" from the pop-up menu. Information about EJS is available at: and in the OSP ComPADRE collection .[/td][/tr]
Just sharing information. ;D