Extracting energy from a permanent magnet

For the discussion of the sciences. Physics problems, chemistry equations, biology weirdness, it all goes here.

Moderators: gmalivuk, Moderators General, Prelates

Soralin
Posts: 1347
Joined: Wed May 07, 2008 12:06 am UTC

Re: Extracting energy from a permanent magnet

Postby Soralin » Wed Jul 17, 2013 2:27 pm UTC

Carnildo wrote:
darryl barton wrote:I am not a scientist but I have made a number of physical and thought experiments involving permanent magnets.

I think of a permanent magnet‘s magnetic field as an active force as opposed to a stable, inactive force

This is where you go wrong. A magnetic field, like a gravitational field, is, in your terms, an "inactive force". Since the rest of your theory is built off of an incorrect assumption, it's meaningless.


Expanding further on that:
darryl barton wrote:My theory is that the common permanent magnets, manufactured and naturally forming have VAST reservoirs of atomic energy lock inside of them, much like fissionable metals but instead of heat, light and partial radiation the permanent magnet‘s reservoir of energy consists of what I call “mazma“.

I also believe that “mazma“ can be accessed / released over a very short period of time, years, month, days, minutes and even seconds as opposed to centuries.

Nope: http://en.wikipedia.org/wiki/Ferromagnetic#Explanation The magnetism of permanent magnets involves a couple aspects of quantum mechanics actually, namely that electrons themselves have a magnetic field, and that in certain materials, they can become aligned.
darryl barton wrote:The following are a few numbers that will demonstrate the crazy amount of potential.

A small, 10lb, neodymium, permanent magnets about the size of a lozenge would exert the equivalent force of 1 horse power (1hp) every 55 seconds (10 pounds x 55 seconds = 550 pounds @ 1 second).

In a 24 hour period said magnet would exert the equivalent force of 26.1818 horse power.
(24 hours x 60 seconds = 1440 seconds / 55 seconds = 26.1818hp)

Over a period of a year, said magnet would exert the equivalent force of 9556.357 horse power. (365 days x 26.1818hp= 9,556.357 hp)

Over a period of a 200 years (theoretical life span of said magnet), said magnet would exert the equivalent force 1,911,271.4 horse power. (200 years x 9,556.357 hp = 1,911,271.4hp). Almost TWO MILLON HORSE POWER form a small, 10lb, neodymium, permanent magnets about the size of a lozenge.

Horsepower does not work that way. The units for horsepower are not pound*seconds, it's foot-pounds/second. A foot-pound, is a pound of force, applied to an object, over a displacement of 1 foot, it's a unit of energy or work, like the Joule. In other words, if something's not being moved, then the horsepower is 0, regardless of the force applied.

And Horsepower is a unit of power, i.e. energy or work over time. 1 horsepower over 1 minute is 1hp, that same amount of power over an hour, is still 1hp, it's just that 1hp for an hour, would be 1 hoursepower-hour(unit of energy, like the joule, or kilowatt-hour), and over a minute, would be 1/60th of a horsepower-hour. Units of horsepower are foot-pounds/second. So foot-pounds/second * seconds, leaves just foot-pounds.

Watts are another unit of power, Joules/second. if you have a 100W light bulb, and turn it on for a second, it uses 100W. 100W for 1 second, is 100 watt-seconds (or 100 Joules). If you instead turn it on for a minute, it's still 100W, it's just that the energy used is now 100W * 60s = 6000J. If you turn it on for an hour, it's still 100W, it's just that the energy used is now 100W * 3600s = 360000 J. (kilowatt-hours are also commonly used instead of joules).

Horsepower and watts are units pf power, which means they're measurements of energy/time, something continuously producing a steady amount of energy, will have a constant horsepower. (Although a magnet isn't constantly producing energy, just applying force isn't enough, everything sitting on your table is applying force, but you can't actually get any energy out of that, unless something moves)

Also:
In a 24 hour period said magnet would exert the equivalent force of 26.1818 horse power.
(24 hours x 60 seconds = 1440 seconds / 55 seconds = 26.1818hp)

What happened to minutes? 1 day is not 1440 seconds. :)
1,440 seconds or 1 horsepower hour

1 hour is also not 1440 seconds.

darryl barton wrote:Q: How far could the average person drive their vehicle on 8,515.98 kilotons of [explosive] energy or almost 1.5 billion watts of electricity?

Those aren't even equivalent units, one is energy, the other is power(energy/time)

darryl barton
Posts: 2
Joined: Tue Jul 16, 2013 6:11 pm UTC

Re: Extracting energy from a permanent magnet

Postby darryl barton » Wed Jul 17, 2013 5:14 pm UTC

Wow, I'm glad that my assumption was incorrect and meaningless.

I stand corected by the current scientific belief system.

There for awahile I thought that the earth's "inactive" gravitational field might "activly" atract some large rock and smash into a Russian city. ;)

User avatar
Copper Bezel
Posts: 2426
Joined: Wed Oct 12, 2011 6:35 am UTC
Location: Web exclusive!

Re: Extracting energy from a permanent magnet

Postby Copper Bezel » Wed Jul 17, 2013 6:11 pm UTC

They all have exactly the same personality. They can't be real.

Edit: Seriously. "I'm not a scientist, but if the scientific establishment won't listen to me...."

And this one's trying to disprove Newton. Not Einstein. Effing Newton.

Per
Rule the second:
Only a small amount of pseudo-science is permitted, mostly to debunk it, and if we feel everything has been said we'll probably lock it (if you're still convinced after 3 pages that 0.999... is not equal to 1 it gets boring)


We have but 114 short posts together, and we'd do well to make the best of the time we have.

Okay, what would you define as an "inactive" force, then? You mention adhesive. I have posters taped to my wall. The adhesive in the duct tape (yes) balances gravity such that the poster neither rises nor falls. If one of the forces is constant and the other is ever-increasing or ... whatever it is that your "active" forces do, then balance would be impossible.

More importantly, the electromagnetic bonds on the small scale work just like the gravitational ones on the large scale, but smaller.

Or consider that a half-meter-tall table seems "static" and a rocket device that hovers at half-meter height seems "dynamic," but something sitting on top of either has exactly the same gravitational potential energy....

What happened to the e-7 in your calculation, by the way? It's not a decoration!
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

she / her / her

User avatar
gmalivuk
GNU Terry Pratchett
Posts: 26816
Joined: Wed Feb 28, 2007 6:02 pm UTC
Location: Here and There
Contact:

Re: Extracting energy from a permanent magnet

Postby gmalivuk » Wed Jul 17, 2013 8:44 pm UTC

darryl barton wrote:I stand corected by the current scientific belief system.
No, you mostly stand corrected by the actual definitions of the words you're using. Even if certain scientific beliefs change, the word "horsepower" still doesn't mean some number of pound*seconds.

You use energy when you hold something off the ground, because that's how muscles work. A table holding that same thing off the ground is not exerting energy, nor would you be if you could to lock all your joints in place using some kind of ratchet system.

Force*time = mass*acceleration*time, which has the same units as mass*velocity, or momentum. Momentum, like energy, is a conserved quantity, but of course having the same units as momentum is not the same as being momentum, nor is simply being another conserved quantity the same as being identical to energy.
Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
---
If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

(he/him/his)

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Thu Jul 18, 2013 2:00 am UTC

Carnildo wrote:
darryl barton wrote:I think of a permanent magnet‘s magnetic field as an active force as opposed to a stable, inactive force

This is where you go wrong. A magnetic field, like a gravitational field, is, in your terms, an "inactive force". Since the rest of your theory is built off of an incorrect assumption, it's meaningless.

Maybe I'm reading more into darryl's comment than is there, but I take the distinction between "active" and "inactive" force as follows:
  • an "active" force is one which is causing an object to accelerate
  • an "inactive" force is one which is not causing any object to accelerate, because it is balanced by other forces, or is causing deceleration.
If this is correct, then darryl is quite right that active forces expend energy (because they do work on objects) while inactive forces do not. That's just classical mechanics 101.

darryl, the bigger problem with what you propose is not that magnets don't store energy (they do), but rather they don't store that much energy. Magnets are manufactured by starting with nonmagnetic metals and magnetizing them. Conservation of energy implies that the amount of energy present in the magnet is no more than the energy required to create it in the first place. This is, needless to say, much less than 8.5 megatons = 35 petajoules of energy you claim. At current energy prices, 35 petajoules would cost several hundred million dollars (even in the cheapest industrial energy market in the country). This would make it hard to manufacture $1 magnets.

Also, please stop confusing units of force with units of energy (force times distance) with units of power (energy over time).
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

screen317
Posts: 252
Joined: Mon May 16, 2011 7:46 pm UTC

Re: Extracting energy from a permanent magnet

Postby screen317 » Sat Jul 20, 2013 2:28 am UTC

skeptical scientist wrote:an "inactive" force is one which is not causing any object to accelerate, because it is balanced by other forces, or is causing deceleration.
Emphasis mine. This makes no sense, since the bolded parts are the same thing.

User avatar
Copper Bezel
Posts: 2426
Joined: Wed Oct 12, 2011 6:35 am UTC
Location: Web exclusive!

Re: Extracting energy from a permanent magnet

Postby Copper Bezel » Sat Jul 20, 2013 2:42 am UTC

Yeah, there's a bit of this there.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

she / her / her

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 3:01 am UTC

screen317 wrote:
skeptical scientist wrote:an "inactive" force is one which is not causing any object to accelerate, because it is balanced by other forces, or is causing deceleration.
Emphasis mine. This makes no sense, since the bolded parts are the same thing.

I was using "accelerate" in its meaning "to cause to move faster" as opposed to "to cause to change in velocity". This should have been obvious from context, so why are you bothering me?
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

User avatar
Copper Bezel
Posts: 2426
Joined: Wed Oct 12, 2011 6:35 am UTC
Location: Web exclusive!

Re: Extracting energy from a permanent magnet

Postby Copper Bezel » Sat Jul 20, 2013 4:08 am UTC

It's still in the wrong category, because accelerating an object against its current path of motion still does work on the object, and that can still be measured in joules. But I really think darryl's misunderstanding is more basic than that.

I think of a permanent magnet‘s magnetic field as an active force as opposed to a stable, inactive force (like a chemical adhesive that can suspend a [1 pound] object for 1 second i.e.1hp=550w simply through the bonding of surfaces).


darryl, what do you feel is the difference between the chemical bonds you mention - which are, after all, electromagnetic forces - and the force of a magnetic or a gravitational field?
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

she / her / her

screen317
Posts: 252
Joined: Mon May 16, 2011 7:46 pm UTC

Re: Extracting energy from a permanent magnet

Postby screen317 » Sat Jul 20, 2013 4:58 am UTC

skeptical scientist wrote:This should have been obvious from context
Clearly not.

Edit:

Besides,

I was using "accelerate" in its meaning "to cause to move faster"
This still means the same as decelerate depending on the reference frame.

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 5:25 am UTC

screen317 wrote:This still means the same as decelerate depending on the reference frame.

Yes, but that's okay, because whether a force is doing work is also dependent on reference frame.
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

User avatar
Tass
Posts: 1909
Joined: Tue Nov 11, 2008 2:21 pm UTC
Location: Niels Bohr Institute, Copenhagen.

Re: Extracting energy from a permanent magnet

Postby Tass » Sat Jul 20, 2013 10:16 am UTC

skeptical scientist wrote:
screen317 wrote:
skeptical scientist wrote:an "inactive" force is one which is not causing any object to accelerate, because it is balanced by other forces, or is causing deceleration.
Emphasis mine. This makes no sense, since the bolded parts are the same thing.

I was using "accelerate" in its meaning "to cause to move faster" as opposed to "to cause to change in velocity". This should have been obvious from context, so why are you bothering me?


If you want to maintain this arbitrary destinction between "passive" and "active" forces, it will lead to a cascade of other terms that will need a creative definition, such as "object".

User avatar
Copper Bezel
Posts: 2426
Joined: Wed Oct 12, 2011 6:35 am UTC
Location: Web exclusive!

Re: Extracting energy from a permanent magnet

Postby Copper Bezel » Sat Jul 20, 2013 11:15 am UTC

I still don't get the work thing, probably because my physics sucks, but if there's a sliding object moving toward me and I push back on it, I'm exerting a force that changes its distance-over-time-squared in inverse proportion to its mass. How does that not qualify as work? The units still check out. They don't if I'm pressing against an immovable object, but there aren't any meters involved there. = /

Still, saying that a magnet "stores energy, but not a lot" is obscuring the point. There's no stored-up magnetic force in a refrigerator magnet that's getting used up in the process of holding it to the refrigerator, and the magnet can be used to produce arbitrarily more work than the energy that went into producing it, for all the same reasons that the Earth can't just up and run out of gravity. = P The fact that a field does work doesn't mean that it gets used up. So what's the connection I'm missing between what you're saying darryl might be thinking and what he actually said?
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

she / her / her

User avatar
gmalivuk
GNU Terry Pratchett
Posts: 26816
Joined: Wed Feb 28, 2007 6:02 pm UTC
Location: Here and There
Contact:

Re: Extracting energy from a permanent magnet

Postby gmalivuk » Sat Jul 20, 2013 12:12 pm UTC

Copper Bezel wrote:if there's a sliding object moving toward me and I push back on it, I'm exerting a force that changes its distance-over-time-squared in inverse proportion to its mass. How does that not qualify as work? The units still check out. They don't if I'm pressing against an immovable object, but there aren't any meters involved there.
Right. What's your contention here?

If you change the kinetic energy of a thing, you're doing work on it. If you hold a static thing for some length of time during which it remains static, you're not doing work on it.

and the magnet can be used to produce arbitrarily more work than the energy that went into producing it
This is not true. If the magnet is not changing the motion of something, it is not producing work. If the motion of something is changing because you're lifting it with the magnet, then the magnet still isn't the thing producing any work.
Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
---
If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

(he/him/his)

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 3:21 pm UTC

I can't believe this thread has lasted this long without anyone posting
Image



gmalivuk wrote:If you change the kinetic energy of a thing, you're doing work on it. If you hold a static thing for some length of time during which it remains static, you're not doing work on it.

To be a little more exact,
Wikipedia wrote:In physics, a force is said to do work when it acts on a body so that there is a displacement of the point of application in the direction of the force. Thus a force does work when it results in movement.

Forces only do work when the force is applied in the direction of movement. (Specifically, work done is the dot product of force and displacement, which is positive when the force is in the direction of displacement, negative when it's in the opposite direction, and zero when it is perpendicular or the displacement is zero.)

gmalivuk wrote:This is not true. If the magnet is not changing the motion of something, it is not producing work. If the motion of something is changing because you're lifting it with the magnet, then the magnet still isn't the thing producing any work.

When a force does work, there is a transfer of energy from the thing doing the work to the object being worked on. For instance, when you carry a bucket up a flight of stairs, you're expending energy doing work, and the bucket is gaining potential energy. When you push a heavy box accross a floor at constant speed, you are doing work on the box, the floor is doing negative work, and there is a transfer of energy from you to the floor (which the floor receives as heat generated by friction).

If you move something using a magnet which remains in contact with the object, you are doing wok on the magnet, and the magnet is doing work on the object, and the net work done on/by the magnet is 0. So there is no net transfer of energy out of the magnet. If the magnet is lifting something up on its own, there would be a transfer of energy. If you could arrange for the magnet to repeatedly do work on another object (for example by turning an electromagnet off and on), it would be transferring energy, and that energy would have to come from somewhere (e.g. a wall socket, in the case of an electromagnet).
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

stianhat
Posts: 175
Joined: Mon Jun 13, 2011 6:31 pm UTC

Re: Extracting energy from a permanent magnet

Postby stianhat » Sat Jul 20, 2013 4:19 pm UTC

skeptical scientist wrote:Forces only do work when the force is applied in the direction of movement. (Specifically, work done is the dot product of force and displacement, which is positive when the force is in the direction of displacement, negative when it's in the opposite direction, and zero when it is perpendicular or the displacement is zero.)


I concur. And dropped in to say that work per definition is dependant on a reference frame. Work is being done either on a system - by the environment or vice versa. Consider it thermodynamically and that will be obvious. A steam engine converts heat to increased pressure, applying force on a piston, which moves creates *positive* work. (if your reference frame borders across the piston)

A more relevant example is the generator, which actually involves magnets spinning around, converting force to electrical work. The magnet is thus just a way of converting force to work, not supplying it.

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 4:43 pm UTC

Tass wrote:If you want to maintain this arbitrary destinction between "passive" and "active" forces, it will lead to a cascade of other terms that will need a creative definition, such as "object".

Not really, no. Work is a standard concept in physics, as I'm sure you well know, and the distinction between forces which do work and forces which don't is neither arbitrary nor problematic. (Though it is, admittedly, reference-frame dependent.)
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

User avatar
Copper Bezel
Posts: 2426
Joined: Wed Oct 12, 2011 6:35 am UTC
Location: Web exclusive!

Re: Extracting energy from a permanent magnet

Postby Copper Bezel » Sat Jul 20, 2013 9:21 pm UTC

gmalivuk wrote:If you change the kinetic energy of a thing, you're doing work on it. If you hold a static thing for some length of time during which it remains static, you're not doing work on it.

skeptical scientist wrote:Forces only do work when the force is applied in the direction of movement. (Specifically, work done is the dot product of force and displacement, which is positive when the force is in the direction of displacement, negative when it's in the opposite direction, and zero when it is perpendicular or the displacement is zero.)

Okay, yeah, that much still makes sense, then.

gmalivuk wrote:This is not true. If the magnet is not changing the motion of something, it is not producing don't getwork. If the motion of something is changing because you're lifting it with the magnet, then the magnet still isn't the thing producing any work.

Yeah, that much I get. I guess I was thinking of a situation where the magnet is held static and something is attracted to it - the same situation as gravity doing work on an object. (You'd "recharge" that system by moving the object back away from the magnet again and storing potential energy, same as with gravity.) What I'm less sure of is this:

skeptical scientist wrote:darryl, the bigger problem with what you propose is not that magnets don't store energy (they do), but rather they don't store that much energy. Magnets are manufactured by starting with nonmagnetic metals and magnetizing them. Conservation of energy implies that the amount of energy present in the magnet is no more than the energy required to create it in the first place.

Is there any connection between the amount of energy used to create the magnet and the potential energy of its attraction to other things? That doesn't quite make sense to me.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

she / her / her

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 10:22 pm UTC

Copper Bezel wrote:Is there any connection between the amount of energy used to create the magnet and the potential energy of its attraction to other things? That doesn't quite make sense to me.

Yes. Think about an unpowered electromagnet suspended 1 foot above a table, and an iron weight sitting on that table. There is no magnetic potential energy here, because the magnet is off. Now flip the switch to turn the magnet on (and, in turn, induce temporary magnetization in the iron weight). You have just created magnetic potential energy where none previously existed, by the simple fact of magnetizing a previously nonmagnetic object. Some of that potential energy will shortly be converted into kinetic energy and then gravitational energy, accoustic energy, and head, when the weight rises up to meet the electromagnet. Conservation of energy implies that the amount of potential energy now present is limited by the amount expended to cause the electromagnet to become magnetized. One manifestation of this is that more powerful electromagnets require more energy.

Although it may at first appear that keeping an electromagnet magnetized requires a constant drain of power, this is only partially correct. In order to keep the electromagnet magnetized, a constant current is required. Because of resistance in the wires, this leads to a constant drain of power which is dissipated as heat, but does not power the magnet. However, when the magnet is first turned on, most of the power drain is not because of resistive heating, but because of magnetic inductance as energy is being stored in the magnetic field. Similarly, when the magnet is turned off, current continues to flow briefly even without external voltage being applied as the energy formerly stored in the magnetic field is released.

Permanent magnets don't work the same way as electromagnets, of course, but energy is likewise stored in their magnetic fields.
Last edited by skeptical scientist on Sat Jul 20, 2013 10:33 pm UTC, edited 1 time in total.
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

User avatar
eternauta3k
Posts: 519
Joined: Thu May 10, 2007 12:19 am UTC
Location: Buenos Aires, Argentina

Re: Extracting energy from a permanent magnet

Postby eternauta3k » Sat Jul 20, 2013 10:30 pm UTC

I think Griffiths' statement of "magnetic forces do no work" is pretty damaging.
VectorZero wrote:It takes a real man to impact his own radius

That's right, slash your emo-wrists and spill all your emo-globin

User avatar
skeptical scientist
closed-minded spiritualist
Posts: 6142
Joined: Tue Nov 28, 2006 6:09 am UTC
Location: San Francisco

Re: Extracting energy from a permanent magnet

Postby skeptical scientist » Sat Jul 20, 2013 10:36 pm UTC

eternauta3k wrote:I think Griffiths' statement of "magnetic forces do no work" is pretty damaging.

Griffith's statement is just plain false. (More accurately, it's true only in the case of simple charged particles.) Magnetic forces do no work on charged particles which do not otherwise interact with the magnetic field, because there the force is always exerted perpendicular to the direction of motion. But magnetic fields definitely do work on magnets. For example, every time you move a compass needle and the Earth's magnetic field pulls it back in the north pointing direction, Earth's magnetic field has done work on the magnet.
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

User avatar
Tass
Posts: 1909
Joined: Tue Nov 11, 2008 2:21 pm UTC
Location: Niels Bohr Institute, Copenhagen.

Re: Extracting energy from a permanent magnet

Postby Tass » Sun Jul 21, 2013 2:17 pm UTC

Technically Griffiths is correct, if you consider permanent magnets due to "bound currents". In all frames you will find that it was an electric force that did the work.

Of course this is largely academic and confusing, especially considering that there is such a thing as a magnetic point dipole. Where is the current in a polarized electron? I'd be more comfortable saying that two electrons have both a magnetic and an electric field, and that both does work when they interact.

User avatar
davidstarlingm
Posts: 1255
Joined: Mon Jun 01, 2009 4:33 am UTC

Re: Extracting energy from a permanent magnet

Postby davidstarlingm » Mon Jul 22, 2013 6:22 pm UTC

darryl barton wrote:I think of a permanent magnet‘s magnetic field as an active force as opposed to a stable, inactive force...a small, 10lb, neodymium, permanent magnets about the size of a lozenge would exert the equivalent force of 1 horse power (1hp) every 55 seconds (10 pounds x 55 seconds = 550 pounds @ 1 second).

No, no, no -- you're doing it wrong.

EVERYONE is going to immediately take (and already has taken) issue with the way you've completely slaughtered units. If you're going to do pseudoscience, make sure at least some of your units work out. The bad science should be hidden in improperly defined forces, not in the unit multiplication itself.

The whole business with horse power is meaningless, since pounds and seconds don't somehow magic into horsepower units. Scrap that approach. You should go with something more sciencey, like "magnetic thrust" or fictitious force multipliers.

For example:

"This neodynium magnet only weighs 10 grams, but it can hold a 0.1 kg weight 1 meter off the floor up against my refridgerator door. Earth's gravity pulls the weight down with about 1 newton of force. Thus, the magnetic thrust is .98 Newtons / 10 grams of magnet or 9.8 Newtons/gram at one meter of height each second, equivalent to 9.8 joules/second or about 10 watts for each gram of the magnet."

Of course, you have to come up with total energy somehow:

"The rare earth magnets used in Voyager 1 have been operating for 35 years and should be able to go up to 50 years or more. Let's say the lifetime is just 40 years, though. That means this little 10 gram magnet has 12,362,112 kilojoules of energy wrapped up inside it."

If you wanted to make it more complex (remember, the more math you have, the more convincing it will seem), add something about integrals and decay rate and half life. You'll end up with a slightly smaller value for total energy, but the added obfuscation will be totally worth it.

Finish off with a grand and nebulous question about the "magnetic thrust potential" if the "latent energy" of a magnet could be released more quickly. Be very careful about the way you shuffle around units. For example:

"The energy density of gasoline is about 45 megajoules/kg, and a fuel efficient car burns around 2 gallons (7.6L) per hour at full speed. So a car needs around 71 kilowatts of power. If we could release that 10 gram magnet's latent energy in a matter of 2 days rather than 40 years, it would only take a dozen of them to run a car continuously for over three weeks on a single magnetic charge. What would that do to the energy crisis?"

Obviously not THAT much harder to debunk, but it seems better-researched and much more impressive.

stianhat
Posts: 175
Joined: Mon Jun 13, 2011 6:31 pm UTC

Re: Extracting energy from a permanent magnet

Postby stianhat » Tue Jul 23, 2013 10:08 pm UTC

davidstarlingm wrote:"The energy density of gasoline is about 45 megajoules/kg, and a fuel efficient car burns around 2 gallons (7.6L) per hour at full speed. So a car needs around 71 kilowatts of power. If we could release that 10 gram magnet's latent energy in a matter of 2 days rather than 40 years, it would only take a dozen of them to run a car continuously for over three weeks on a single magnetic charge. What would that do to the energy crisis?"


Ooh, here you can actually insert something like ... "and this is why the big oil lobby is working against it, pulling strings to make sure my invention never gets the academic attention it merits!"

A whiff of conspiracy makes pseudo science so much harder to disprove, since you can just claim that any opponent is "trying to hide the truth"...

User avatar
davidstarlingm
Posts: 1255
Joined: Mon Jun 01, 2009 4:33 am UTC

Re: Extracting energy from a permanent magnet

Postby davidstarlingm » Wed Jul 24, 2013 1:29 am UTC

stianhat wrote:Ooh, here you can actually insert something like ... "and this is why the big oil lobby is working against it, pulling strings to make sure my invention never gets the academic attention it merits!"

A whiff of conspiracy makes pseudo science so much harder to disprove, since you can just claim that any opponent is "trying to hide the truth"...

Just imagine what that would do to the energy crisis. But of course THEY don't want us doing that kind of research. Too much profit to be made....

User avatar
Minerva
Posts: 947
Joined: Sat Nov 11, 2006 2:58 pm UTC
Location: Australia
Contact:

Re: Extracting energy from a permanent magnet

Postby Minerva » Sun Aug 04, 2013 10:03 am UTC

Avian wrote:
zalzane wrote:A magnetic field does not store energy.

Guys at CERN also thought so, until a faulty coil caused the field of one of their superconducting magnets to collapse and blew a 10-ton machine apart :?


An electromagnet (superconducting or not, doesn't really matter for our purposes here) stores energy in its magnetic field. (Note that electromagnet and inductor are synonymous in this context.)

However, we're talking about permanent magnets here - it's important to distinguish a permanent magnet from an electromagnet.

Vaniver wrote:That should work (though you're also recapturing a lot of the energy spent moving the magnet).


You're not extracting energy from the magnet. You're doing work moving the magnet, and converting that energy to electrical energy.

Diadem wrote:But that would mean that God, er, Griffith, is wrong.


And Man invented Jackson, and Man killed God.
...suffer from the computer disease that anybody who works with computers now knows about. It's a very serious disease and it interferes completely with the work. The trouble with computers is you play with them. They are so wonderful. - Richard Feynman

User avatar
Tass
Posts: 1909
Joined: Tue Nov 11, 2008 2:21 pm UTC
Location: Niels Bohr Institute, Copenhagen.

Re: Extracting energy from a permanent magnet

Postby Tass » Mon Aug 05, 2013 3:26 pm UTC

Minerva wrote:
Avian wrote:
zalzane wrote:A magnetic field does not store energy.

Guys at CERN also thought so, until a faulty coil caused the field of one of their superconducting magnets to collapse and blew a 10-ton machine apart :?


An electromagnet (superconducting or not, doesn't really matter for our purposes here) stores energy in its magnetic field. (Note that electromagnet and inductor are synonymous in this context.)

However, we're talking about permanent magnets here - it's important to distinguish a permanent magnet from an electromagnet.


Not really. The field contains the same energy. (density B2/2mu) regardless of origin.

Put a permanent magnet in a coil, heat it above the Curie temperature and you get a current spike, same as if you switched off the current in a primary coil.

To re-magnetize it you'd have to expend energy. Of course it is in no way viable as an energy storage device since both the cycle efficiency and the energy density are terrible.


Return to “Science”

Who is online

Users browsing this forum: No registered users and 4 guests