Ejs Open Source Charge Particle in Magnetic Field B Java Applet in 3D
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1800.msg7327#msg7327  Created by prof Hwang Modified by Ahmed
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1450msg5484;topicseen#msg5484 Created by prof Hwang

Charge In B-Field
This 3D Ejs Charge particle In B-Field model allows the user to simulate a moving charged particle in two identical uniform magnetic fields separated by a zero magnetic field gap. A charge moving in a magnetic field experiences a magnetic force given by the Lorenz force law
[center] $\vec{F}=\vec{v}\times\vec{B}*q$ = v*B*q*sin(theta) [/center]
where theta specifies the angle between the velocity vector v and the magnetic field B. In this simulation, the velocity and B-field are perpendicular (theta = 90 degrees) and the force is maximum and perpendicular to both v and B as predicted by $\vec{v}\times\vec{B}$. You can adjust the magnitude of the magnetic field B, the mass m and charge q of the charged particles. The slider at the top controls the width of the field free region (it is a percentage of half the window width). The magnetic field is assumed to be uniform $Bz\hat{z}$ inside the magnet region. and the field is zero when outside the boundary.
You can change the location and velocity of the charged particle with mouse drag and drop or with sliders.

/htdocs/ntnujava/ejsuser/14019/users/sgeducation/lookang/chargeinNS_pkg/chargeinNS.propertiesFull screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
Download EJS jar file(1318.4kB):double click downloaded file to run it. (60 times by 30 users) , Download EJS source View EJS source

activities adapted from 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

1 When $Bz\hat{z}$ is positive and the charge particle is completely inside the $Bz\hat{z}$ field region, which way do positively charged particle circle (clockwise or counter-clockwise as view from the top looking down).  Use the Fleming left hand (thumb Force, second finger B field and middle finger current i ) or right-hand cross product rule $\vec{F}=\vec{v}\times\vec{B}*q$ to determine if the field points into or out of the screen?
2 Explain why particle traveling in the region without B field, travel in a straight path.
3 Charged particle that remain in the uniform B magnetic field (orange color field vectors) experience uniform circle motion. Why? What provides the centripetal force?
4 design an experiment to investigate systematically, in a table the data and effects of varying the charge particle mass, m and charged q.
5 Do they experience the same force F?
6 What accounts for particle moving in circles of different radii (for the ones that stay in the uniform magnetic field)?
7 How can you change the different parameters to decrease the radius? Explain why each change results in a smaller radius.
8 challenging Optional: If you have EJS installed, modify this model to simulate a cyclotron. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/cyclot.html It may be useful for you to know that Model ->Initialization page to see how the initial position and velocity of the particle(s) is(are) set as well as looking at the Model-> Custom page to see the equations of motion for a particle in the magnetic field as well as the gap region.