Third Law of Motion and Magnetic Force: Is There a Connection?

AI Thread Summary
The discussion explores the relationship between Newton's Third Law of Motion and magnetic forces, particularly in the context of electric motors. It is established that while magnetic forces can seem to violate the Third Law, the electromagnetic field itself carries momentum to ensure conservation. The nature of magnetic force is clarified as an interaction between moving charges, with an emphasis on quantum electrodynamics. Participants suggest that understanding these concepts may require further reading or experimentation, such as observing how electromagnets function. Overall, the conversation highlights the complexity of magnetic forces and their foundational theories in physics.
magmash
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Hi

does the Third law of motion have any thing to do with the magnetic force

like in a electric motor ?
 
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The 3rd law on the general level means momentum conservation, which always applies. In the case of magnetic interactions it is sometimes less obvoius. Do a search on 'recoil of a railgun'.
 
Welcome to PF;
The short answer is "yes".
Did you have a specific example in mind?
 
Well the magnetic force violates the third law, hence it was recognized that the electromagnetic field itself must also have momentum to compensate and conserve momentum in the system.
 
Simon Bridge said:
Welcome to PF;
The short answer is "yes".
Did you have a specific example in mind?

Yes

The movement of electrons
 
I am not able to find any information on what the magnetic force really is
Is it some thing that science can't really explain at the mean time, like example what exactly causes Gravity
 
magmash said:
I am not able to find any information on what the magnetic force really is
Is it some thing that science can't really explain at the mean time, like example what exactly causes Gravity

No the theory of magnetism has been around for a long time, and so has the theory of gravitation.
Magnetism is just a force exerted on moving charges by other moving charges. (Or if you're into that magnetic monopole stuff, magnetic charges as well)
 
any more info ?
 
The magnetic force is part of the electromagnetic force - which is understood, in the standard model, in terms of interactions between charged particles, such as electrons, and photons. You should look up "quantum electrodynamics".

note: "movement of electrons" is too vague - can you be specific?
i.e. can you think of some situation in which the motion of an electron in a magnetic field appears to violate the third law?
 
  • #10
Simon Bridge said:
The magnetic force is part of the electromagnetic force - which is understood, in the standard model, in terms of interactions between charged particles, such as electrons, and photons. You should look up "quantum electrodynamics".

note: "movement of electrons" is too vague - can you be specific?
i.e. can you think of some situation in which the motion of an electron in a magnetic field appears to violate the third law?

Well what I mean is,

example when we spray water at an object let's say a standing piece of plywood, the ply wood will fall down due the the force of the water particles hitting the plywood, Well how does the magnetic force work ? is there any atom,particle collisions causing the force ?
 
  • #11
magmash said:
Well what I mean is,

example when we spray water at an object let's say a standing piece of plywood, the ply wood will fall down due the the force of the water particles hitting the plywood, Well how does the magnetic force work ? is there any atom,particle collisions causing the force ?

Thre are four known forces, and the electromagnetic is one of those. When you spray water various forces come into play.

I suggest you read a high school textbook on electromagnetism http://en.wikipedia.org/wiki/Electromagnetism

If you do some simple experiments it becomes more obvious. eg electromagnets, deflection of a compass by current in a wire.
 
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  • #12
magmash said:
Well what I mean is,

example when we spray water at an object let's say a standing piece of plywood, the ply wood will fall down due the the force of the water particles hitting the plywood, Well how does the magnetic force work ? is there any atom,particle collisions causing the force ?
OK - so you don't want to talk about electrons then?

The principle is that a photon is transferred or exchanged between charges.
So the quickie answer to your question is "yes - there is a particle collision involved"... though, on the scale of photons, "collision" is not the right word...

See:
http://van.physics.illinois.edu/qa/listing.php?id=414
http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html

It is difficult to know how to answer your questions, or even what you are asking, properly, since you won't tell us where you are coming from. Presumably you have seen magnets work right? So what are you asking? What level are you asking from?
 
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