Thread: Magnets

I was doing and expieriment with Neodymium magnets, (witch can hold up to 5,000 their own weight) and when i heated one to 260C in my oven, when it came out and cooled one pole was stronger then the other. when I put another magnet close to it, i felt the normal same-pole repulsion, just reduced. but when they got within 2 cm of each other, they attracted each other!

My conclusion was the North pole on the heated magnet, which i had observed earlier as stronger than the south pole, attracted the other magnet's south pole and overcame it's weaker side. ive heard that it is impossible for a magnet to be stronger on one side, so do you have any idea how this could have happened?

it is impossible.

youre most likly just thinking it is but really isnt or something is disturbing it. exacly what i cant think of right now

THis can simply be accounted for by either a fracture near one of the poles, or [more likely] the area of the poles is different, how do you know which magnet exhibits this?

Poles must be equal and opposite in strength, flux density however could be different. I.e. magnetic flux spread out at one pole, and thus more concentrated at the other.

I'm only just studying this at an Australia highschool now, so if my reasoning is incorrect please let me know.


Jack Heron

No you are about right just like water if it's going at high pressure throuh a pipe and the pipe opens out the flow rate and pressure remain constant, but the speed at which the water is moving decreases. if you have a magnet with different poles sizes the flux at the smaller pole is more concentrated.

When a star collapses into a black-hole, its gravity is such that the field is left behind. I wonder if it is possible for a magnetetic field to be so strong that once the magnet is somehow removed, the field remains.

yes, in fact, there is a formula for this very thing, it applies to all magnets. The speed at which the field collapses, or disappears is a function of the receding velocity of the magnet from the point where the field was.

Originally Posted by Megabrain

THis can simply be accounted for by either a fracture near one of the poles, or [more likely] the area of the poles is different, how do you know which magnet exhibits this?

First off, Neodymium magnets shatter when they are cracked or hit. second, I know which magnet exibits this because when i tried a non-heated magnet against another non-heated magnet, they were normal, but the third, heated magnet attracted it. I had bought 4 penny-sized Neodymium magnets for this.

Originally Posted by Zelos

it is impossible.

youre most likly just thinking it is but really isnt or something is disturbing it. exacly what i cant think of right now

you might think it is impossible because you are u probobly used to normal magnets that are very weak. I, on the other hand, was working with Neodymium magnets that lift 1300 times its own mass. When I took one the size of a penny, it could lift a 2-liter bottle with 1650 millileters in it. I think that Neodymium magnets exhibit different properties than normal, weak magnets.

also, from Wikipedia-

A neodymium magnet or NIB magnet (also, but less specifically, called a rare-earth magnet) is a powerful magnet made of a combination of neodymium, iron, and boron — Nd2Fe14B. They have replaced marginally weaker and significantly more heat-resistant samarium-cobalt magnets in most applications, due mainly to their lower cost. These magnets are very strong in comparison to their mass, but are also mechanically fragile and the most powerful grades lose their magnetism at temperatures above 80 degrees Celsius. High-temperature grades will operate at up to 200 and even 230 °C but their strength is only marginally greater than that of samarium-cobalt.

Neodymium magnets should always be handled carefully. Some that are slightly larger than the size of a penny are powerful enough to lift over 10 kilograms. They are hazardous; able to interfere with pacemakers and implanted heart devices with deadly consequences [1]. An NIB's magnetic force increases with the size of the piece of ferromagnetic metal and larger neodymium magnets can severely pinch skin or fingers, or even break bones when suddenly attracted to a magnetic object. Operating a large neodymium magnet close to smaller magnetic objects (keys, pens, etc.) and larger magnetic surfaces (radiator or a car, for example) can be dangerous if the person is caught between the magnet and the magnetic object or surface.

Neodymium magnets are made with special powders and coatings, so they are very fragile. They are often plated with a metal such as nickel. The magnets can fracture at temperatures over 150 °C, or under impact as a result of their own acceleration. When this happens, the magnets break apart so suddenly that flying pieces can cause injury.

END WIKIPEDIA

I was using magnets that were treated not to fracture at high temeratures. if they had, they would have shattered.

Originally Posted by chamilton333

I was doing and expieriment with Neodymium magnets, (witch can hold up to 5,000 their own weight) and when i heated one to 260C in my oven, when it came out and cooled one pole was stronger then the other. when I put another magnet close to it, i felt the normal same-pole repulsion, just reduced. but when they got within 2 cm of each other, they attracted each other!

My conclusion was the North pole on the heated magnet, which i had observed earlier as stronger than the south pole, attracted the other magnet's south pole and overcame it's weaker side. ive heard that it is impossible for a magnet to be stronger on one side, so do you have any idea how this could have happened?

My money is that you realligned the magnetic domains of the magnet when you heated it. Who told you that a magent cant have one pole stronger then the other - it would just have a lot of internal stress due to the attraction of the poles.