Magnetic Field from 2 wires

The EJS Magnetic Field from 2 wires model computes the B-field created by an electric current through 2 straight wires in the z direction with the options of external magnetic fields. The user can click on any part of the 2D space to plot the magnetic field lines.

  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, edited by lookang using the Easy Java Simulations (EJS) modeling tool . Additional exercises written by lookang. 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:

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