Maker Fair

Magnetism Explorations

Magnetism Exhibits

Silent Collisions, Collide magnets on a pencil. For 40 years I bounced magnets on a pencil until a seventh grade student opened my eyes to a world of possible experiments. If you can find a pencil with a steel eraser, a donut magnet will hold on to the steel. A dropped magnet will collide with it creating an elasric or inelastic collision dpending on pole orientation.

Freefall Magnets, Drop magnets on a horizontal rod and observe their friction free interaction.

Magnetic Atmosphere Model, a stack of magnets on a pencil models the behavior of atmospheres.

Magnets 3 vs 1 Feel the force between two film cans, one contains 3 magnets, the other contains 1 magnet and clay to make its mass identical.

Garden of Magnets Donut magnets just fit inside film cans. Two of them inside a filmcan will make the film can float. The cans can be made to repel each other as well as other magnets placed around a tray of water.

Magnets Round the Rim set two disk magnets to attract when rim to rim, try to make one orbit the other.

Electric current model Place 5 donut hole magnets around the rim of a donut magnet and model electric current flow.

Magnetic car, build it and roll it.

Magnet jump, Make a pile of three donut magnets. On the rim pile two donut hole magnets and keep one aside. Slide the donut holes down into the hole, they will be pushed out at first. Push them down until the stick. Drop a third donut hole magnet onto the pile of magnets you just created. All three donut holes will leap up and land on the rim.

Quantitative force between two magnets versus distance, Use a digital scale to measure the force law between magnets.

Gaussian Accelerator, Magnets and steel ball bearings can be used to accelerate the balls.

Magnets as Compasses, magnetic fields

Where's North? Chinese Compass , Hang ten identical magnets and they will all point in the same direction.

Magnetic Poles Explore attraction and repulsion of north and south magnetic poles.

Magnetic Globe, Embed a neodymium magnet inside an earth globe to model the magnetic field of the earth.

Pierson Oscillator, One magnet can be used to levitate the edge of another magnet. This shows the need for replacing poles with magnetic field lines.

The invention of Neodymium Magnets. As physicists you can make discoveries that change the world. A Physics teachers your students can go on to make discoveries that change the world. Of course your students return 20 years later having gained 40 pounds, with less hair on their heads and more on their chins and say, "Hi Prof. Doherty, remember me?" My student Chris Thrush was on the team at GM research labs that invented neodymium magnets.

Eddy Currents

Eddy Current slowing , Snack, Drop a Neodymium Magnet down a copper tube or slot and it will slow due to the magnetic fields from eddy currents. At the museum we made the motion of the magnets visible by dropping them down a slot with one open side.

Forever Falling Magnets, allow neodymium magnets to slide on a rotating disk and they will make interesting orbits. One neat thing is that adding multiple magnets made neat sounds as they hit the edge of the exhibit.

The "Forever Falling Magnets" exhibit.
Spin the disk and eddy currents pull the magnets up against gravity.
They then fall and make interesting orbits.

Guided magnetic Roller, Roll a neodymium disk magnet down a roadway made of aluminum and eddy currents will steer the magnet along the roadway.

Floating in Copper, Eddy currents in thick copper can be used to slow down the motion of magnets so that human eye hand feedback can "fly " one magnet under another.

Drop a neodymium magnet onto copper chilled to liquid nitrogen temperatures. The eddy currents will repel the dropped magnet with a force greater than gravity.

Eddy current propagation in time. Gorazd Planinsic showed me an interesting exhibit in which a neodymium magnet is placed under a spinning aluminum disk. Iron filings placed on a plastic holder above the spinning disk show the time delay for the eddy currents to propagate through the spinning disk.

Diamagnetism

Repel a Grape, A torsional oscillator made from two grapes can be used to show that grapes are diamagnetic.

Repel a Flame, The paramagnetic attraction of a neodymium magnet for atmospheric oxygen can be used to repel an oxygen depleted flame by buoyancy effects.

Magnets in Fluids

Ferrofluid. You can make your own ferrofluid by burning steel wool and collecting the black iron oxide bits then mixing them into corn oil. You can also buy magnaflux powder at welding shops, or use a dull knife to scrape the iron oxide coating off cheap VCR tapes. First stretch the VCR tapes to double their length to weaken the glue bond then pull them across a dull knife held in a vise.

Modern uses for magnetism

Magnetic Tape, Strips of cassette ape can be magnetized to show how digital computers work.

Magnetic Feedback, A pickup coil attached to an amplified speaker can create a feedback loop which can be modulated by inserting metals into the loop.

Barkhausen Effect, A Radio Shack Amplified Speaker and an iron core pickup coil, can be used to produce the barkhausen effect.

Electromagnetism

Stripped down generator, A magnet falling through a coil of wire can create enough current to light an LED.

Induction, A coil of wire driven by a radio can be used to drive the tape head of a cassette player.

Reference Books:

Klutz Magnetism Book: Magnetic Magic by John Cassidy and Paul Doherty

Square Wheels: by Don Rathjen and Paul Doherty

 Scientific Explorations with Paul Doherty © 2007 17 May 2007