We will show you a massive neodymium permanent magnet assembly weighing more than half a ton. Also, check out permanent magnet chair we built: [ Ссылка ]
These magnets are made of rare earth elements represents the strongest class of permanent magnets. In this video, we first will see what happens when you approach it with ferromagnetic materials (like steel), and then afterward we will explore how conductive metals behave in a strong magnetic field.
Here is a wrench and a scale for measuring the pull of magnet which reaches 25 kg while the wrench itself is only 1 kg. On larger ferromagnetic objects attraction can easily reach hundreds of kilograms.
Next up is a hammer! Note that I added 5 cm (2 inches) layer wood so not to damage the surface and to be able to easily remove it. Even with this added distance pull force is around 40 kg.
Afterwards, a flexible iron sheet is placed to the magnet which illustrates the distance where objects are visibly attracted. On larger ferromagnetic objects attraction can easily reach hundreds of kilograms.
The permanent magnet of such size is stronger than the earths magnetic field in a radius of 4 meters around it and can turn screens of a laptop from 1.5 meters. Ferromagnetic objects from iron are drawn to magnet form half a meter away as illustrated with iron sheets.
We continue experiments with placing a ferrofluid on the magnet. This reveals the spikes on the surface. These spikes are acting (pointing) like magnetic field lines so in a sense you can visualize the magnetic the direction and strength of the magnetic field. Sometimes the camera loses focus because of the strong magnetic field interferes with electronics and sensors. The ferrofluid contains very tiny magnetite particles, which act as tiny magnets and when the external field is applied they aligned in “spiky” structures pointing in the direction of the magnetic field vector. When in close proximity to poles the magnetic forces dominate over gravity making so the fluid can defy gravity. If I were to let, go the container it would fly towards the pole of the magnet to the spot with the highest magnetic field intensity.
Next up we take 4 kg copper sheet and when we throw it towards the magnet it rapidly slows down. When the plate is getting closer to the magnet it moves noticeably slower. All that happens because of the induced current in the copper sheet. Copper is an excellent electrical conductor and when it is moved in a magnetic field, the changing flux creates eddy currents according to Maxwell’s-Farady’s law of induction. In short, these currents create an opposing magnetic field and overall damps movement of copper and that is why it is extremely difficult to move the copper sheet next to a magnet.
And this simple demonstration perfectly showcases the effect of opposing forces caused by induction. Normally plate of such size would fall down in a second, however, since it is placed in a strong magnetic field (which changes in the plate during fall) it takes almost 20 seconds for it to hit the ground.
In the end for a bigger effect, we took a 20 kg copper sheet and rolled it in a cylinder and which we dropped on the magnet. The first attempt was with a couple of centimeter gap. The copper sheet is slowed down up until it reaches the center of the magnet. At that point, the magnetic flux becomes negative and current changes direction. In the second attempt, we shrunk the gap to 5 mm. In both cases, it is overwhelmingly slowed down by induced currents.
Credits to:
Antra Gaile & Mikus Mīlgrāvis for assistance with video production
Viesturs Šints for sourcing the ferrofluid
Toms Beinerts for sourcing the magnet
● Music Released and Provided by Tasty
● Song Title: Konac - Away
● Music Video: [ Ссылка ]
● Label Channel: [ Ссылка ]
Made and narrated by researcher Reinis Baranovskis
