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Coulomb Force Wrong

screen shotscreen shot
Screen shots of two-three charges with force vectors.LEFT is EJSS and Right is EJS

Coulomb Force Wrong Model

The EJSS Coulomb Force Wrong model asks students to figure out what is wrong with the model with multiple charges with force vectors shown. Users can change charge of an individual charge and add more charges. Users can examine and correct the model if EjSs is installed. 


  1. Run the simulation. Move the charges around and observe the force vectors (as well as the magnitude of the force). What is correct about the model?  What is your evidence?
  2. Use the slider to change the charge of one of the charges (the size of the charge also changes to remind you that you changed the charge). The drop down menu allows you to select the charge (by color) that you want to change. What is wrong with the force vectors and/or magnitude reading? What is your evidence? Add at least one additional charges, using the Add Charge button, to confirm your answer.
  3. If you have EJSS installed, now that you have determined what is wrong with the model, correct it.  The mistake is in Model->Custom->Calculate Force. Describe how you fixed it. (Background needed: arrays and for loops or see EJSS Computing Basics.)


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


The Coulomb Force Wrong Model was created by Anne Cox, Wolfgang Christian,and Francisco Esquembre using the Easy JavaScript Simulations (EJSS) authoring and modeling tool. Exercises written by Anne J Cox, Darren Tan and lookang.


Using the EJSS authoring toolkit installed here, Select "A EJSS digital Library", in Library select "JS EJS model in Singapore", double click folder "05electricitynmagnetism_11efield", and double click filename "CoulombForceWrong" and click button "Download". Save the model source code inside your EJSS defined workspace/source/

Information about EJSS is available at: <> and in the OSP ComPADRE collection <>.



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Software Requirements


Android iOS Windows MacOS
with best with Chrome Chrome Chrome Chrome
support full-screen? Yes. Chrome/Opera No. Firefox/ Samsung Internet Not yet Yes Yes
cannot work on some mobile browser that don't understand JavaScript such as.....
cannot work on Internet Explorer 9 and below



Francisco Esquembre, Wolfgang Christian, Anne J Cox; remixed to JavaScript by lookang

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  WebEJS ready 20231007

Sample Learning Goals


For Teachers

Title: Exploring Electrostatics with Interactive Simulations: Unveiling Errors in the Easy JavaScript Simulation EJSS Electric Field Package


Originally developed by Anne Cox, Wolfgang Christian, and Francisco Esquembre, the EJS Electric Field: What is Wrong? Package has been rejuvenated through the efforts of lookang, who updated it to JavaScript. This package encompasses a range of electrostatics models, each intentionally embedded with errors. By manipulating charges and observing resulting forces and electric fields, users engage in a dynamic process of error identification and correction. This blog post highlights the features, accessibility, and applications of this educational resource.

Package Contents:

The package enables users to interact with various charge configurations, witness electric field patterns, and track test particle motion, all while discerning errors within simulations. It empowers users to examine, modify, and rectify simulations using the EJSS authoring toolkit download and run A supplementary overview of essential programming concepts for fixing models is also provided.


Easy JavaScript Simulations (EjSs):

This package was constructed using the Easy JavaScript Simulations (EjSs) modeling tool, a pivotal component of the Open Source Physics Project. Distributed as a compiled HTML5 zip file, the simulations can be launched in modern browsers supporting JavaScript. EjSs facilitates the accessibility, customization, and generation of computer models, enhancing user engagement in the realm of physics education.


Accessing and Implementing:

Users can initiate the simulations by clicking on the provided link: [Launch Incorrect Physics Sim" The browser compatibility with JavaScript determines successful launch. Furthermore, the Open Source Physics Project offers a plethora of additional Ejs and EJSS models, fostering a rich repository of interactive educational resources.


Educational Impact:

This resource's significance extends beyond its interactive nature. The methodology of error-driven learning encourages critical thinking, problem-solving, and understanding of electrostatic concepts. This approach aligns with modern pedagogical trends, promoting active learning, productive failure and effort and exploration.


Journal Article Reference:

The educational potential of these resources is comprehensively discussed in the journal article titled "The Physics Teacher" (Vol 49, No 5, p. 273-276). The article delves into the practical utilization of these simulations and their impact on physics education. [Read the full article here"

In conclusion, the revitalized EJSS Electric Field: What is Wrong? Package, transformed into JavaScript by lookang, offers an engaging platform for students and educators to delve into electrostatics. By uncovering errors within simulations, users not only enhance their conceptual grasp but also cultivate essential problem-solving skills. This initiative exemplifies the evolution of pedagogy through technology, propelling physics education into a dynamic and interactive realm.

email: This email address is being protected from spambots. You need JavaScript enabled to view it. for the password to the Corrected version 






Other Resources by Professor Wolfgang, Francisco and Anne

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