changes made

1. color scheme
2 magnet NS text and position
3 B field visual start at edge of magnet for ease of associating the influence of F = q.v^B where ^ is cross product.
4 rearrange the bottom panel
5 add z and vz into the evolution page and values display for http://link.aip.org/link/?AJP/65/726/1 journal article has this student learning challenge (Bagno & Eylon, 1997)

The question is the paper is:
The velocity of a charged particle moving in a magnetic field is always perpendicular to the direction of the field.

The responses:
37% think it is true,
The reasons and interviews analyzed indicated that the causes are:
a. Recitation of formula: v, B and F are always perpendicular according to left hand or right screw law 81
b. No reason 19
reference:
Bagno, E., & Eylon, B.-S. (1997). From problem solving to a knowledge structure: An example from the domain of electromagnetism. American Journal of Physics, 65( 8 ), 726-736. doi: 10.1119/1.18642

My thoughts:
but the answer is false. it could be a supposition of uniform velocity and circular motion, thus there is an angle =! 90o between v and B, much like a helix path



6 add Force display value  F = q.v^B
7 activate the 3 axes coordinate system for ease of communicate and associating motion to x y z direction

other good resources:
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1431.0 Charged particle motion in static Electric/Magnetic field by Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=36 Charged particle motion in E/B Field JDK version by Fu-Kwun Hwang
http://www.opensourcephysics.org/items/detail.cfm?ID=8984 Charge in Magnetic Field Model written by Fu-Kwun Hwang
edited by Robert Mohr and Wolfgang Christian
http://www.opensourcephysics.org/items/detail.cfm?ID=9997  Charge Trajectories in 3D Electrostatic Fields Model written by Andrew Duffy
http://www.opensourcephysics.org/items/detail.cfm?ID=8996 E x B Trajectory Model written by Anne Cox
http://www.compadre.org/osp/items/detail.cfm?ID=8984 Charge in Magnetic Field Model written by Fu-Kwun Hwang edited by Robert Mohr and Wolfgang Christian