could magnets be used to create a renewable source of energy?

[WouldBe]

It's no different from something sitting on a shelf indefinitely. There's no energy being used.

Fridge doors are normally vertical while shelves are normally horizontal.

If no magnetic energy was being used the magnet would not stick.

Where does the 'energy input' come from to keep the magnet recharged?

 

[In Bloom]

A physics type once mentioned something like this to me, something about the magnets spinning until the whole thing just blew apart or formed a black hole or sommat. Does anybody here have a clue I could borrow?

 

[Good Intentions]

Isn't it a DC motor? Made them in GCSE physics but can't remember whether they were DC or AC.

A motor and a dynamo are basically the same thing. In a motor electricity gets added to get movement out, in a dynamo movement is added to get electricity out. The process is reversable.

 

[Poi E]

Why?

A fridge magnet (not the mod variety) will stick to a fridge door indefinately. Work is being done to over come gravity. So where does the energy input come from?

It won't stick indefinately. Particles in a magnet eventually become aligned or unaligned or something and they lose their magnetic potential energy.

 

[FridgeMagnet]

Fridge doors are normally vertical while shelves are normally horizontal.

If no magnetic energy was being used the magnet would not stick.

Where does the 'energy input' come from to keep the magnet recharged?

What's the difference between the magnet being attracted by the metal and a tin being repelled by a shelf? They're both forces. In fact it's magnetic repulsion between atoms that keeps the tin from falling through the shelf.

Nothing's getting hotter, or accelerating, or emitting radiation, or anything like that, and the magnet's gravitational potential energy isn't changing, there's no energy transfer. (Actually it's the friction on the metal that's stopping the magnet moving downwards, which depends on the attractive magnetic force - so it's not *quite* the same thing as the shelf, the attractive force is acting perpendicular to gravity.)

I think there might be some confusion here as to conservation of energy.

 

[Good Intentions]

Fridge doors are normally vertical while shelves are normally horizontal.

If no magnetic energy was being used the magnet would not stick.

Where does the 'energy input' come from to keep the magnet recharged?

There is no magnetic energy the same way there is no gravitational energy. The magnet gives out unlimited energy the way the earth gives out infinite energy. Choose the way you want to describe energy being expended and be consistent, and you'll see why it's impossible.

 

[xes]

A physics type once mentioned something like this to me, something about the magnets spinning until the whole thing just blew apart or formed a black hole or sommat. Does anybody here have a clue I could borrow?

funny you should mention black holes,I watched a prog on scifi one night,a guy who was some expert in back engineering foreign technology,claimed to have been recruited by the bods at area 51 (yes,I watch some utter bollocks) he mentioned that the "alien" technology he tried to back engineer,worked by spinning round really fast,like a turbine,ripping a hole in time.

Wow,just think. i could have just invented time travel aswell as solved wold peace

 

[WouldBe]

Actually it's the friction on the metal that's stopping the magnet moving downwards

But if a magnet were stuck to the underside of a metal shelf the same would not apply.

 

[Good Intentions]

But if a magnet were stuck to the underside of a metal shelf the same would not apply.

The force would still be perpendicular to the area it works on, so then it is exactly like a tin sitting on a shelf. The magnetism holding the magnet up is stronger than gravity pulling it down.

 

[ICB]

Direct contact?

In a motor electricity gets added to get movement out, in a dynamo movement is added to get electricity out.

Movement then.

 

[WouldBe]

The magnetism holding the magnet up is stronger than gravity pulling it down.

So work is being done.

 

[Good Intentions]

Depends on how you define work:

1)Work is only done if movement takes place.

2)Work is done here in exactly the same way work is done by the earth's gravity

Both approaches lead to the same conclusion - no perpetual energy.

 

[FridgeMagnet]

So work is being done.

No, because there's no movement.

http://en.wikipedia.org/wiki/Mechanical_work

 

[Crispy]

Glue something to the underside of a shelf and it stays there! Amazing! What keeps it up? It's the attraction between a bunch of atoms, that's what! Even though atoms are almost entirely made of empty space and never actually 'touch' they still manage to hang together and keep things stuck to the underside of shelves. It's a fundamental force. Know what that force is?

Electromagnetism (the other three are gravity, the strong nuclear force you find in reactors and the weak nuclear force which you'll never need to know about because it's so weak)

Magnetism is just a manifestation of that force, just like atoms hanging around in molecules. It can also hold things to the underside of shelves.

 

[WouldBe]

No, because there's no movement.

http://en.wikipedia.org/wiki/Mechanical_work

If you stick a piece of iron to a magnet it becomes magnetised.

To become magnetised the dipoles in the iron are re-aligned to that of the magnetic field.

Movement does therefore occur so work is done.

 

[FridgeMagnet]

Not while it's just sitting there....

 

[oneflewover]

A motor and a dynamo are basically the same thing. In a motor electricity gets added to get movement out, in a dynamo movement is added to get electricity out. The process is reversable.

And used all the time in electric trains and pump storage power stations.

On trains motors are reversed to put power back to the overheads. Pump storage power stations use hydro power to generate electricity and when there is spare electricity they change and pump water back into the resevoir.

 

[blamblam]

Would it be possible to create a renewable source of energy by harnessing the power of magnets?

I'm thinking more along the lines of magnet repulsion. If you can get magnets to spin against eachother,they would carry on spinning indefinatly,would it then be possible to harness this energy created by the spinning motion?

No. Sorry

 

[xes]

No. Sorry

I'll show AALLLL OF YOU!!!

Then you'll be sorry, Mwahahahahahahahaaaa

 

[gurrier]

If you stick a piece of iron to a magnet it becomes magnetised.

To become magnetised the dipoles in the iron are re-aligned to that of the magnetic field.

Movement does therefore occur so work is done.

Nah. At small enough levels everything is moving all the time. Work from classical mechanics only comes into play when the whole body is displaced and doesn't have too much meaning at a sub-atomic level.

A magnet doesn't fall because the electromagnetic force is greater than the gravitational force on the magnet. It requires an extra input of force (producing work) to pull the magnet away from the fridge.

As it happens, this is a textbook example of the weakness of gravity as compared to the other fundamental forces. The electromagnetic force generated by the piddly little fridge magnet (does that count as dissing the mods?) is greater than the gravitational force generated by the entire planet.

 

[WouldBe]

Nah. At small enough levels everything is moving all the time. Work from classical mechanics only comes into play when the whole body is displaced and doesn't have too much meaning at a sub-atomic level.

Maybe 'work' isn't the right term to use or the scientific definition is too narrow.

A magnet doesn't fall because the electromagnetic force is greater than the gravitational force on the magnet. It requires an extra input of force (producing work) to pull the magnet away from the fridge.

If you made a small electro magnet with built in battery of the same power as a fridge magnet and stuck it to a fridge it wouldn't stay stuck for anywhere near as long as a permanent magnet.

While the electro magnet is stuck to the fridge door, 'work' is being done due to electrons moving round the circuit generating the magnetic field and clearly energy is being lost as the battery wil go flat.

So if producing a magnetic field results in 'work' being done in an electro magnet then why not in a permanent magnet? and if so where does the energy come from to supply the permanent magnet.

Also if a permanent magnet of the same strength as an electro magnet lasts considerably longer then permanent magnets are a better storage of energy than batteries.

But enough of fridge magnets.

If you have a magnet on a low friction surface and bring another magnet with the same pole close to the first magnet, the first magnet will be repelled and move away. Clearly work (by any definition) is being done as motion occurs.

If the magnets are carefully shaped and positioned why couldn't you get a rotor of magnets to spin inside a ring of fixed magnets?

Some of this rotational energy could be taped off to turn a dynamo.

 

[Juice Terry]

If you have a magnet on a low friction surface and bring another magnet with the same pole close to the first magnet, the first magnet will be repelled and move away. Clearly work (by any definition) is being done as motion occurs.

Er yeah the work is being done by your muscles which are fuelled by chips and stuff. The magnet doesn't just move towards the other one on its own does it?

 

[WouldBe]

Er yeah the work is being done by your muscles which are fuelled by chips and stuff. The magnet doesn't just move towards the other one on its own does it?

I was actually talking about magnets repelling each other.

If you drop the magnet close enough to the first they will still repel each other. You are not doing the work then are you?

ETA:

Do you manually have to turn the needle in a compass so it points north? Or is the 'work' done by magnetic forces?

 

[Good Intentions]

We didn't say magnets are incapable of producing work. We're saying it's incapable of providing perpetual energy. For exactly the same reasons gravity can't, because magnetism and gravity are exactly the same type of force.

 

[WouldBe]

Gravity does provide a source of perpetual energy in the form of hydro electricity.

Who said magnets would provide perpetual energy?

Someone has already pointed out earlier that magnets do get weaker over time. So when a magnet becomes 'flat' it will no longer repel another magnet.

It just appears to me that magnets are far more efficient at storing energy.

Depending how easily it would be to 'recharge' the magnets would determine how efficient the system was overall.

Don't forget that magnetised rock (lodestone) occurs naturally.

 

[stdPikachu]

Gravity does provide a source of perpetual energy in the form of hydro electricity.

I realise you did a , but that's merely a renewable source. The enrgy in this equations is ultimately provided by the sun - it evaporates water and causes it to rise and then fall as rain to be collected in lakes. All the dams and magnets do is convert to potential energy of the lake into movement, from which the magnets convert into eletrical potential. Simple enough really

Magnetite is formed from iron-rich rocks which are magnetised by the earths magnetic field, which is driven by whatever it is that creates our own magnetic field - mostly radioactive decay in the earth's (iron rich) core making it move about (although last I saw no-one was quite sure).

And magnets don't "store" energy. They merely influence certain other types of energy directed at them.

 

[Good Intentions]

Gravity does provide a source of perpetual energy in the form of hydro electricity.

No, it doesn't. It takes more energy for the water to go back up above the turbines. We don't have to put the energy into the system (the sun does), but it's far from perpetual.

Who said magnets would provide perpetual energy?

xes jokingly asked if it could.

Someone has already pointed out earlier that magnets do get weaker over time. So when a magnet becomes 'flat' it will no longer repel another magnet.

Natural permanent magnets are a small and largely insignificant subset of magnets.

It just appears to me that magnets are far more efficient at storing energy.

How? It takes ridiculous amounts of energy to charge something magnetically so it will last.

 

[WouldBe]

And magnets don't "store" energy. They merely influence certain other types of energy directed at them.

Set up 2 rigid thin bars hinged at the top ( a bit like a gold leaf electroscope). Attach a magnet to the end of each bar with similar poles facing each other so that they repel.

The bars will open-up some distance depending on the strength of the magnets. 'Work' is being done to over come gravity which is trying to close the bars together. The bars will stay in this state for ages. As 'work' is being done 'energy' is being used, the 'energy' coming from the magnets, so magnets store 'energy'.

 

[WouldBe]

No, it doesn't. It takes more energy for the water to go back up above the turbines. We don't have to put the energy into the system (the sun does), but it's far from perpetual.

Perpetual means it keeps on going without stopping. So unless you remove all the water from the planet or stop the sun shining then hydro electric is perpetual.

How? It takes ridiculous amounts of energy to charge something magnetically so it will last.

Magnetically charged lodestone has been lying around on the planet for millenia and comes for free.

You can make a permanent magnet by stroking a magnet along a piece of iron so "ridiculous" amounts of energy aren't required.

 

[stdPikachu]

As 'work' is being done 'energy' is being used, the 'energy' coming from the magnets, so magnets store 'energy'.

Work is not being done, gravitational force is merely in equilibrium with magnetic force.

Perpetual means it keeps on going without stopping. So unless you remove all the water from the planet or stop the sun shining then hydro electric is perpetual.

...but since the planet will run out of water, and the sun will stop shining, it's not perpetual, is it?

Magnetically charged lodestone has been lying around on the planet for millenia and comes for free.

You can make a permanent magnet by stroking a magnet along a piece of iron so "ridiculous" amounts of energy aren't required.

...but you can't get any energy out of your "free" magnets except by doing work on them (i.e. moving them about).