Magnets

[the_lone_wolf]

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

Recently bought a bunch of tools from Halfords and their "Industrial" tool cabinets

Bought myself a magnetic tray, and instead of having it take up drawer space it's being stored stuck to the side of the cabinet

Now...

Something bothers me...

My mind wonders where the energy to hold the tray up is coming from? Are the magnets losing their power at an increased rate than they would if the tray was stored on a shelf?

Or am I making a mistake assuming that holding the tray against gravity's pull requires an energy cost...

[davepoth]

the_lone_wolf said:

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

Recently bought a bunch of tools from Halfords and their "Industrial" tool cabinets

Bought myself a magnetic tray, and instead of having it take up drawer space it's being stored stuck to the side of the cabinet

Now...

Something bothers me...

My mind wonders where the energy to hold the tray up is coming from? Are the magnets losing their power at an increased rate than they would if the tray was stored on a shelf?

Or am I making a mistake assuming that holding the tray against gravity's pull requires an energy cost...

I was going to say "go to university and study physics" but that clearly won't help.

Non-electro-Magnetism is caused by electrons rotating around a nucleus in an atom. To simplify a lot, in most materials the atoms are disorganised, so the effect cancels itself out. In iron, the atoms are regularly arranged in such a way that the atoms spin in in an organised fashion, causing a field. Magnetism is effectively the two bits of iron trying to organise each other.

[otolith]

the_lone_wolf said:

Or am I making a mistake assuming that holding the tray against gravity's pull requires an energy cost...

Yes.

Nothing's moving and nothing's getting hot!

[Simpo Two]

Think of magnetism as omnidirectional short-range gravity... then turn your head sideways. Owzat?

[-Pete-]

That's a very good question, my mind is now boggling (A-Level Physics and an MSc Hons) do magnets lose their magnetism through 'magneting'?

I made the last word up.

ETA: Probably Magnetting?

[the_lone_wolf]

otolith said:

the_lone_wolf said:

Or am I making a mistake assuming that holding the tray against gravity's pull requires an energy cost...

Yes.

Nothing's moving and nothing's getting hot!

Sounds about right...

Thought that would have to be it...

[dodgyviper]

otolith said:

the_lone_wolf said:

Or am I making a mistake assuming that holding the tray against gravity's pull requires an energy cost...

Yes.

Nothing's moving and nothing's getting hot!

Except for the force carriers, which transfer the force through motion.

[Flibble]

-Pete- said:

That's a very good question, my mind is now boggling (A-Level Physics and an MSc Hons) do magnets lose their magnetism through 'magneting'?

Yes, though the rate of loss is pretty small. Otherwise all those magnetic perpetual motion machines would actually work!

[hairykrishna]

the_lone_wolf said:

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

A physics graduate? From where? No work is being done. No 'energy cost'.

[Einion Yrth]

hairykrishna said:

the_lone_wolf said:

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

A physics graduate? From where? No work is being done. No 'energy cost'.

Really quite similar to hanging it from a hook.

[the_lone_wolf]

hairykrishna said:

the_lone_wolf said:

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

A physics graduate? From where? No work is being done. No 'energy cost'.

Hence my above post about me thinking the same thing...

But your reply is greatly appreciated...

[Krikkit]

hairykrishna said:

the_lone_wolf said:

Should probably start by saying I'm a Physics graduate so feel free to talk techincally to me!!

A physics graduate? From where? No work is being done. No 'energy cost'.

Probably a bit harsh - magnetism is one of the harder things (imo) that you can study in an undergrad degree. At least with QM you know it doesn't make proper sense before you start!

[hairykrishna]

Krikkit said:

Probably a bit harsh - magnetism is one of the harder things (imo) that you can study in an undergrad degree. At least with QM you know it doesn't make proper sense before you start!

Not being funny, but this isn't exactly some complicated electromag problem. It's a basic conception question about energy and force in classical physics.

Anyway - seems he just needed a bit of prodding to remember the basics.

[Marf]

the_lone_wolf said:

f-ckin' magnets, how do they work?

http://tinyurl.com/383qdom

Edited by Marf on Wednesday 2nd January 13:59

[Tony2or4]

The force holding the magnet up is friction between the magnetic tray and the side of the tool box: if the 2 surfaces were perfectly smooth (zero friction) then the magnetic tray would slide down the side of the toolbox, whilst staying in contact with it all the way down. (Might be possible to create this effect by putting some Castrol GTX twixt the 2 surfaces.)

For friction to work, though, there has to be a normal contact force between the 2 surfaces, and this contact force is basically the magnetic force of attraction.