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Magnetic Field From Loops

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 <>.



Code Language Translator Run

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



Fu-Kwun Hwang, Wolfgang Christian, Robert Mohr remixed by lookang (This email address is being protected from spambots. You need JavaScript enabled to view it.); Fremont Teng; Loo Kang Wee

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Sample Learning Goals


For Teachers



Combo Box and Sliders

Toggling the combo box will give you their respective sliders


Toggling Full Screen

Double clicking anywhere in the panel will toggle full screen.

Play/Pause and Reset Buttons

Plays/Pauses and resets the simulation.






Other Resources


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