Friday, February 27, 2015

Neodymium Magnet Induces Eddy Current In Aluminum Tube



This experiment shows Eddy currents (Foucault currents) effect when a Neodymium magnet is moving inside aluminum tube. The moving magnet produces very low voltage, but with very high amperage Eddy current. The voltage measured up to 0.8 volts when aluminum tube is connected to a digital multitester while the magnet is moving.

The magnet is fallen slowly inside alluminum tube as Eddy current creates magnetic field in alluminum tube that holds magnet againts gravity force. Magnet diameter is 34 mm, while aluminum hole diameter is 35 mm. Closer distance from magnet to aluminum wall means greater Eddy current. Thicker tube wall means greater Eddy current, so greater force against gravity when magnet falls.

This magnet effect occurs to any electric conductor material with no magnetic attraction, such as: alluminum, copper, brass, bronze, etc.

This phenomena is usually applied to magnetic brake, the brake that doesn't use friction, and also magnetic clutch. It is also called: Eddy current brake, induction brake, electric brake, electric retarder. The kinetic energy produced by the brake when slowing down the speed will be converted into heat, not by friction, but because of the heat from the Eddy current.



Neodymium Magnet Menginduksi Arus Eddy Dalam Tabung Allumunium

Percobaan ini memperlihatkan efek arus Eddy (arus Foucault) ketika magnet Neodymium bergerak dalam tabung aluminium. Gerakan magnet menghasilkan tegangan yang sangat rendah, tetapi dengan arus Eddy dengan ampere yang sangat tinggi. Tegangan terukur hingga 0,8 volt ketika tabung aluminium terhubung dengan multitester digital dan magnet digerak-gerakkan.

Magnet yang dijatuhkan di dalam tabung aluminium akan bergerak perlahan karena arus Eddy yang timbul menciptakan medan magnet di tabung aluminium sehingga menahan magnet terhadap gaya gravitasi. Diameter magnet 34 mm, sedangkan lubang tabung aluminium diameter 35 mm. Semakin dekat jarak dari magnet ke dinding aluminium berarti semakin kuat arus Eddy. Semakin tebal dinding tabung akan semakin besar arus Eddy, sehingga akan lebih kuat melawan gravitasi ketika magnet jatuh.

Efek magnet ini terjadi untuk setiap bahan konduktor listrik tanpa daya tarik magnet, seperti: alluminum, tembaga, kuningan, perunggu, dan lain-lain.

Fenomena ini biasanya diterapkan pada rem magnetik, rem yang tidak menggunakan gesekan, dan juga kopling magnetik. Dinamakan juga sebagai: rem arus Eddy, rem induksi, rem listrik, retarder listrik. Energi kinetik yang dihasilkan rem saat memperlambat kecepatan akan dirubah menjadi panas, bukan karena gesekan, tapi karena panas oleh arus Eddy.


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