Tag: cool

plsdontrecognizeme:

the-british-pineapple:

weirdsciencefacts:

A magnet slows down on the way through the metallic pipe because of the magnetic induction Lenz’s Law

I thought this was the phenomenon where a copper (a non magnetic metal) still affects magnets?

Different metals have different magnetic effects. Iron is ferromagnetic, meaning it aligns to have the same magnetic field as a magnet affecting it (i.e, it becomes attracted to the magnet). Other non-ferromagnetic conductors gain an induced magnetic field.

The principle behind this is that a moving charge produces a magnetic field, so a loop in a conducting wire does as well, since conducting wires carry moving charges. However, a conducting wire without any current moving in it will generate its own current when a magnetic field is brought near it; but currents also generate magnetic fields! So, the original magnetic field makes a current in a wire which makes its own magnetic field.

Lenz’s Law tells us that this induced magnetic field will always oppose the change in magnetic field. So, if you bring a positive magnetic pole near a loop of wire, the wire will produce a current that generates a negative current. This effect slowly declines as the field stays there, but will in fact REVERSE if the field is taken away. Remember: it opposes the CHANGE in field. So take away the positive pole, and your induced field will go positive!

How this applies to the copper tube, is very similar! The magnet is basically making the tube induce an opposing field, which pushes up on the magnet, while gravity pushes down. This is because the tube is essentially a very wide wire. The falling magnet without a tube there would ordinarily accelerate due to gravity, but with the tube giving an opposing force, it reaches a terminal velocity that’s actually pretty slow.

The reason copper is used is because copper is an excellent conductor. This is the same principal that allows hoverboards to work over liquid nitrogen-cooled superconductors. The low resistance in the metal allows the current to flow freely, and in the case of the superconductor, the opposing field can be so strong as to oppose gravity and allow levitation!

(This was in my physics class last year I’m just very excited that I know something relevant!)