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Bar Magnet, Compass, and Magnetic Field Lines Interactive

The red and green rectangle in this interactive represents a bar magnet. The smaller, red and green diamond represents a compass needle. Drag the compass needle around to explore the magnetic field surrounding the bar magnet.

Red represents the north magnetic pole of both the bar magnet and the compass needle. Green represents the south magnetic pole of both the magnet and the needle.

This interactive makes use of Java software. If you cannot see the interactive, you may not have Java on your computer.

Walter Fendt, April 20, 2001

The original version of this applet can be found at Walter Fendt's web site at www.walter-fendt.de/ph11e/mfbar.htm. Other Java applets by Walter Fendt related to physics topics are available at www.walter-fendt.de/ph11e.

When you click on the magnetic needle and hold down the mouse button, a magnetic field line through the center of the compass needle is drawn in blue. When you release the mouse button, the field line is "frozen" in place. You can draw additional field lines by clicking on the compass needle and dragging it to a new position.

Arrows along the magnetic field line show the direction of the field. By convention, magnetic field lines "flow" from the north pole of a magnet to its south pole, in the direction that the north pole of the compass needle points.

Click the "Clear field lines" button to erase all of the field lines you have drawn so far and start over with a "clean slate".

Click the "Turn magnet" button to flip the bar magnet so the directions of its magnetic poles are reversed.

Interactive link Interactive animation: Bar Magnet & Compass (using Flash software)

Interactive link Interactive animation: Earth's Magnetic Field

Interactive link Earth's North Magnetic Pole interactive

Activity link Activity: Build a Magnetometer and use it to detect magnetic fields!

Last modified February 20, 2008 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA