This is a Java tutorial, which requires that you have Java, a
free software, installed on your computer. It works best if you
have the latest version of Java installed. If you are having
trouble viewing or using this tutorial, try downloading the
latest version of Java. Magnetic fields are produced by electric
currents; a simple segment of current-carrying wire will
generate around it a circular magnetic field in accordance with
the right hand rule. You can create a stronger magnetic field by
taking wire and forming it into a coil; the field is more
concentrated in the center of the loop than outside the loop. By
adding more loops to a coil, you create an increasingly stronger
magnetic field. Stacking multiple loops also concentrates the
field even more; this arrangement is known as a solenoid. Iron
filings are often used to reveal the shape of magnetic fields,
as in the tutorial below. In the presence of a magnet, these
filings will rearrange themselves according to the magnetic
lines of force (flux lines).