Screen shot of the dipole and test charge.

# Dipole Trajectory Wrong Model

The EJS Dipole Trajectory Wrong model shows the electric field generated by a dipole. A slider can change the separation between the charges. A test charge moves in the dipole field, but its trajectory is incorrect. Users can examine and correct the model if Ejs is installed.

## Exercises:

1. Run the simulation and observe the dipole field due to fixed charges (red and blue) . Also note the trajectory of the test charge.* You can move the test charge anywhere on the screen (except on top of one of the stationary charges). You can also change the separation between the two fixed charges.
2. What is wrong with this simulation? What is your evidence?
3. If you have EJS installed, now that you have determined what is wrong with the model, correct it. You will need to go to Model->Evolution to make the changes. Describe how you changed it and how you verified your work.

*Recall that a test charge is defined to feel the effects of an external electric field, but not change the field itself (therefore, there are no field vectors around it).

### References:

- Giancoli, Physics for Scientists and Engineers, 4th edition, Chapter 21 (2008).

### Credits:

The Two Charges and Detector Model was created by Anne J Cox, Wolfgang Christian, and Francisco Esquembre using the Easy Java Simulations (EJS) authoring and modeling tool. Exercises written by Anne J Cox.

You can examine and modify a compiled EJS model if you run the program by double clicking on the model's jar file. Right-click within the running program and select "Open EJS Model" from the pop-up menu to copy the model's XML description into EJS. You must, of course, have EJS installed on your computer.

Information about EJS is available at: <http://www.um.es/fem/Ejs/> and in the OSP ComPADRE collection <http://www.compadre.org/OSP/>.