How do bar magnets work? (More complicated. READ DESCRIPTION.)?

Question

Since magnetic fields and magnetic force are caused by motion relative to an electric field, how can a static bar magnet create a magnetic field and exert a magnetic force on another static object, and how can a magnetic force from a bar magnet do work when magnetic force cannot do work? (Bar magnets can do work with magnetic force. If you stick a bar magnet to another bar magnet, and then lift it, the magnetic force between the two does work by lifting the second magnet and giving it gravitational potential energy.) Also, please do not use the word "moment" in your explanation, because I do not yet understand the concept of magnetic moment.

Answer 1

Magnetism is the WAKE of a moving electron in time space like a moving boat in water. Electricity running through a wire will generate a magnetic field around the wire.----Coil the wire around a few times and the magnetism will add up with each coil--making a useful electromagnet.



Electrons ALSO move AROUND the nuclei of atoms making small magnetic fields, not big enough to be of any notice.---In most substances the electrons spin in all sorts of directions around a jumble of atoms---CANCELING OUT any net magnetic effect.



But in some forms of metal blocks of atoms form what are called "domains" where all the atoms are lined up. Thus the electrons spinning makes each domain noticeably "magnetic"---BUT alas, usually thes domains are also "jumbled up" randomly too, canceling out any magnetic effects.



HOWEVER Some Irion and some other metals can be made into MAGNETS by heating them and exposing them to a high voltage magnetic field as they cool down----The heat frees up the jumbled domains from their places, and the high voltage causes the domains to all line up--and freeze that way when the metal cools---Forming a magnet----All the magnetic domain blocks are in line and the magnetic forces enforce each other.--we have a bar magnet.

Answer 2

The short answer is that there are moving electrical charges within a permanent magnet, they just circulate within the domains of the magnetic material itself.



Magnetic charges are created by moving electrical charges and where the movement creates a length contraction through Special Relativity. The SR's length contraction makes certain charges (i.e. negative or positive) less dense or more dense than the other charge within a given volume of the magnetic material.



https://youtu.be/hFAOXdXZ5TM

Answer 3

Energy can be stored in many ways.

It takes energy to line up the magnetic domains to form the magnet.

That energy IS available to do work.

Now if you bring a piece of steel nearby and the magnet attracts that steel it does some work.

But you then try to pick up some paper clips with the result. It can't pick up anywhere near as many so we know that the field has been reduced.

Every time the bar magnet does work the resultant field is lessened.



Of course if you pull the steel away the magnetic field strength is restored.

But then you have put the energy back into the field by doing work on the magnet.



To that extent the magnets do no net work other than the work that is stored in them by their very creation.



In your example of one magnet lifting another the magnet does NOT do work.

There is no movement between the magnets so that it exerts a static force .

Work = force * distance = force * zero = no work.

what DOES do work is whatever is lifting your first magnet.

Answer 4

Magnets exists with both a north and south pole. If a magnet is placed next to another, it can reinforce or neutralize its neighbor depending on their orientation. All matter consists of subatomic materials. All have a magnetic nature. Most materials have subatomic materials all with random orientation. Should the sub microscopic magnets align, they reinforce each other and a magnet results. Magnets have their sub microscopic magnets aligned.

Answer 5

The "static" bar magnet is made up of atoms, and atoms have moving parts.

Answer 6

EDIT



A simple example of how “'magnetic fields do no work” is not always true.



Imagine 2 particles with *opposite” charges connected by a rigid rod. The charges are moving away from you (‘into the screen’).



[+Q]---[-Q]



A magnetic field acts to the right →.



The force on +Q is downwards. The force on -Q is upwards. This makes the system start to spin, so rotational kinetic energy is gained (work is done by the magnetic field).



This happens because the particles (charges) are connected.



END EDIT

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The electrons in an atom can be thought of as spinning charges, orbiting around a nucleus. (Though this isn't really accurate in quantum mechanical terms, but it will do.)



Each 'spinning' electron produces a small magnetic field. The orbital motion also produces a magnetic field, but spin’s field is the main one.



In iron (and a few other elements), the spins of some electrons in neighbouring atoms can get aligned in the same direction. We then get an overall magnetic field equal to sum of the fields from the aligned electrons.



So the ‘motion’ you are looking for is the ‘spin’ of the electrons.

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How magnets do work is a much harder question. This gets this regularly discussed at length and it causes many arguments. E.g. https://www.physicsforums.com/threads/work-done-by-magnetic-field.31239/



My opinion is:

The statement that 'magnetic fields do no work' *only* applies to classical, freely moving point charges. This means quantum mechanical effects, such as what ‘force’ holds an electron in place in an atom, can’t be taken into account.



There are many situation where 2 magnetic field can interact and do work, e.g. 2 bar magnets being attracted). That situation is not comparable in any way to a freely moving point charge in a magnetic field.



Just my opinion though.

Answer 7

Nope - motion relative to an electric field doesn't create a magnetic field. At least not that simply. Rather, the voltage induced in a closed circuit is proportional to the rate of change of the magnetic flux it encloses (can't post the formulas here, so check them out in the source below) - and vice versa. The important thing here is that it's about change, and a closed circuit loop.



As for the magnetic field doing work - yes, after a fashion. Unfortunately (for the perpetuum mobile builders, mostly - not so much for people building or using all kinds of electric motors or generators), that work is almost 100% recoverable. Meaning, you can't get any work out a magnetic field that you didn't put into it at some place.



In the case of one magnet pulling up a second magnet (slightly different from your example), the work is done by reducing the energy in the combined magnetic field of these two magnets - and you have to put it back into the field when you pull the two magnets apart.

Answer 8

You have the first bit backwards:

Currents are caused in a conductor by motion relative to a magnetic field.



Magnetic fields do not require motion.





Your example of using one magnet to lift another also has a misconception.

You are joining two items together - the fact that it is by magnetism rather than bolting them is irrelevant - it is then YOU that provide the energy / work to lift the lower object, just as if it were mechanically fixed to the top one.



The difference with two stuck-together magnets is that then you have to pull them apart, rather than simply removing a fixing.