Eddy Current Braking

These rare-earth magnets are extremely powerful (likely N52 grade neodymium). Keep them away from pacemakers, credit cards, electronic devices, and computer storage media. The magnetic field can damage or erase electronic equipment within several inches. Store magnets separated by substantial distance to prevent them from attracting violently.

These magnets are brittle and will shatter if dropped from excessive height or if they collide with each other. Broken magnets expose inner nickel-plated surfaces that present inhalation and ingestion hazards. The neodymium-iron-boron material can oxidize and produce toxic dust. If a magnet breaks, carefully collect all fragments using gloves, seal in a container, and dispose according to institutional hazardous material protocols. Never allow broken magnets to remain accessible.

Purpose

Students observe Lenz's law in action: a rare-earth magnet rolls at constant (very slow) velocity down a copper ramp while a non-magnetic cylinder accelerates normally. A second configuration shows a magnet falling in slow motion onto a thick copper block. Both dramatically illustrate velocity-dependent eddy current braking.

Copper plank inclined on a wooden block, with a cylindrical magnet and stainless steel cylinder at the top and a clear plastic catch box at the bottom

Thick copper block with a disk magnet wrapped in blue tape and a thin metal stem, sitting on the copper surface

Figure 1: The rolling magnet setup shows the copper plank raised at an angle on a wooden block, with both magnetic and non-magnetic cylinders for comparison demonstrations.

Figure 2: The dropping magnet setup features a thick copper block that dramatically slows the fall of the rare-earth magnet through induced eddy currents.

Warning: Powerful Magnet Hazards

Warning: Magnet Breakage and Toxic Materials

Purpose

Safety Warnings

Warning: Powerful Magnet Hazards

Warning: Magnet Breakage and Toxic Materials

Purpose