The Demonstration: An aluminum ring is launched off of an electromagnet. With the iron bar in the electromagnet, it goes even higher.
Quick Physics: An electromagnet is just a
coil of wires with a current running through it. Electrons are like
tiny magnets and when they move (as in a current), they create a
magnetic field. The iron core increases the magnetic field of the
electromagnet. The ring feels a greater magnetic force, which
pushes it higher. The colder the ring it, the less resistance there is
and the more current can flow through it. More current means a bigger
magnetic field and the ring goes even higher!
The jumping ring makes a metal ring jump up into the air using an electromagnet like the one described earlier. It is actually two electromagnets in one. Wire is wrapped around a base made of iron. The wire is connected to the electricity and when current flows in the wire, the iron becomes a very strong magnet. The second magnet is a metal ring. It sits on top of the iron base. The magnetic field from the iron in the base causes electricity to flow around through the ring. The electricity in the ring is called an eddy current. The eddy current causes the metal ring to become a magnet. The two electromagnets are arranged so that their north poles point at each other. Two north poles repel each other, so the base and the ring push each other away. Since the ring is very light, it gets pushed up into the air.
When you add an additional iron bar into
the electromagnet, it increases its strength. (This is why we used a
nail in the previous electromagnet experiment.) A stronger magnet makes
the ring jump much higher! If you add a second ring, you might expect
it not to go as high because there is twice as much mass. But, there is
also twice as much ring to turn into a magnet that will be repelled and
it launches just as high.
We can make the ring jump much higher by
using liquid nitrogen to make it very cold. When things are very cold,
electricity can flow more easily. Since the electricity can flow
through the ring better, the ring becomes a stronger magnet and jumps a
If the ring gets cut, it wonÕt jump. We
said some of the electricity in the wire gets into the ring to make it
into a magnet. But, electricity has to flow in a complete circle to
make a magnet. Since there is a cut, the electricity canÕt get all the
way around. The cut keeps the ring from turning into a magnet.
Link to Teacher Resources
Page Updated 8/29/07