Awesome Magnet Tricks - Eddy Currents

Did you know that metals such as copper and aluminum can interact with a magnet?

Suspend a strong neodymium magnet by taping a string to its sides. Start it swinging like a pendulum. Slide a thick piece of aluminum under the swinging magnet. Why does it stop?!

Note that the magnet does NOT touch the aluminum plate. The experiment is then repeated with a thick block of copper.

As the magnet sweeps across the metal, it pushes on the electrons, creating eddy currents. Those eddy currents give rise to their own magnetic field, rapidly braking the magnet. (Magnetic brakes!)

The better the conductor, the stronger the braking action.

Credits: Music by Kevin MacLeod

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Tags:

• Electricventures
• awesome
• science
• trick
• physics
• demonstration
• stunt
• neodymium
• magnet
• electricity
• experiment

[KyleJamesComedy]

Show me how you found green laces. That's a better trick.

[ElectricVentures]

@KyleJamesComedy LOL Actually chose the green string on purpose, as it seemed to give the clip more visual interest. I believe it was a string from a name badge. The point of the demo, however, is to illustrate that there are interactions between moving magnets and metals that a magnet would not pick up. (Most people are not aware of this.) Glad you enjoyed the laces!

[adamcowan1]

you should make it clear that the magnet isn't attracted to those metals without relative motion, otherwise it's not very impressive at all

[ElectricVentures]

@adamcowan1 Good point. It is interesting that so many visitors don't know which metals a magnet will stick to (eg: iron, nickel), or which metals a magnet will not stick to (most metals, including copper and aluminum). For those that are aware, however, seeing the swinging magnet slow over aluminum is often a revelation.

For those "in the dark", note that my earlier video "The Aluminum Pie Tin Experiment" demonstrates how various metals interact with a magnet ... or better: try it yourself!

[nametyj]

Is tis related to eddy current?

[ElectricVentures]

@nametyj Yes, indeed! Moving a magnet near any metal will produce eddy currents in the metal. Those eddy currents give rise to their own magnetic fields. (Magnetic fields are created by moving electric charges.) As a result, even "non-magnetic" metals such as copper can interact with a strong magnet.

[ElectricVentures]

@irishdrummerlad: Its hard to tell if you are just joking, or don't actually know that magnets do not pick up copper and no not pickup aluminum. Indeed there are few very metals that magnets will actually pickup! Try picking up aluminum foil with a magnet! Doesn't work! --Take it from another drummer!

[pixilash1]

.......................

[ElectricVentures]

@ElectricVentures Continued: The moving electrons (eddy currents), give rise to their own magnetic field, that interacts with the moving magnet.

[ElectricVentures]

@NinjaAssassin336 Sometimes it seems like magic! ;-) I believe you meant "electrostatically charged", as in having a net "negative" or "positive" charge! You can rule that out, as the pieces were grounded when I touched them.

Nonetheless, magnets do interact with the charged objects! In a metal, the protons (+) are pretty much locked in place, but lots of electrons (-) are free to move. As the magnet moves, it pushes/pulls on those charged objects. The moving electrons (continued)

[NinjaAssassin336]

@ElectricVentures Whoo percussionists! But the aluminum could've been electromagenticly charged....I believe magnets work because the electrons in the charges are attracted to each other or something like that. Could be sorcery.