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TranslatorsCafe.com Unit Converter. Magnetomotive Force

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Изучаем технический английский с помощью видеосюжетов многоязычного Конвертера единиц TranslatorsCafe.com!

Hello and welcome to the Translators Cafe.com channel! I will demonstrate the Barkhausen effect.
We will hear the sound caused by rapid changes of size of magnetic domains in a piece of iron.
For this experiment we use a strong neodymium magnet. The coil is connected to the recording device.

Now we can hear clicks because of the Faraday effect. If a magnetic field rapidly changes, it induces the current, which is converted to the sound.
An aluminum tube is placed into the coil. Aluminum is paramagnetic; therefore we cannot hear any sound.
The brass rod gives the same results because it is also paramagnetic. Paramagnetics are attracted by an externally applied magnetic field. They form induced internal magnetic fields, which have the same direction as the direction of the applied magnetic field.
Now we place a soft iron core into the coil. Iron is ferromagnetic. The sound is produced by slowly moving a magnet toward the solenoid core and away from it. This sound is caused by the domains, which are aligning themselves along the magnetic field when this field is slowly changes. This effect was discovered by German physicist Heinrich Barkhausen in 1919 and is caused by rapid discrete changes of size or rotation of magnetic domains, which are similarly magnetically oriented clusters of atoms.
Now we place a steel bolt into the coil. The hissing sound is much weaker than we heard when we tried a soft iron rod because the steel is more resistance to magnetizing than the soft iron.
In another experiment we will show how diamagnetics and some paramagnetics interact with magnetic field. Please subscribe to our channel!

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