Magnetism - "Stopping Time"

Standards

NSES Content Standard B - Physical Science: Light, heat, electricity, and magnetism - Grades K-4

Young children begin their study of matter by examining and qualitatively describing objects and their behavior. The important but abstract ideas of science, such as atomic structure of matter and the conservation of energy, all begin with observing and keeping track of the way the world behaves. When carefully observed, described, and measured, the properties of objects, changes in properties over time, and the changes that occur when materials interact provide the necessary precursors to the later introduction of more abstract ideas in the upper grade levels.

Misconceptions

• All metals are attracted to a magnet

• All silver colored items are attracted to a magnet.

• All magnets are made of iron.

• Larger magnets are stronger than smaller magnets.

• The magnetic and geographic poles of the earth are located at the same place.

• The magnetic pole of the earth in the northern hemisphere is a north pole, and the pole in the southern hemisphere is a south pole.

• Only magnets produce magnetic fields.

• A magnetic field is a pattern of lines (not a field of force) that surrounds a magnet.

• In a magnet, the magnetic field lines exist only outside the magnet.

• Magnetism is a permanent property of a material

Activity

An old illusion that has become more popular with the availability of neodymium. This very powerful magnet can create some very powerful illusions. The simplest is “Stopping Time” (Magicity.com, product number 11-3799 ‘size small,’ $26.95). The magician borrows an analogue watch with a moving second hand from a volunteer. The magician takes the watch and places it across their hand, says some magic time stopping words and stops time. A few more magic words and time starts again.

The illusion is that the magician is wearing an neodymium ring. The powerful magnet is strong enough to stop the second hand on the analogue watch without doing any permanent damage. There are more advanced versions that utilize the magician’s ability to palm coins. If you are able to learn this, the possibilities are endless.

It’s not magic, it’s science!

This “trick” focuses students’ attention on the ideas that lager magnets are not always stronger magnets, magnetism can be induced, and magnets emit a magnetic field that affects objects within it.