When two objects Attract/Repel(Charges/magnets/electromagnets/etc )

  • Thread starter Phztastic
  • Start date
In summary, forces of attraction or repulsion between two objects are mutual, meaning both objects experience the same strength force in opposite directions. This is known as Newton's third law. Even if one object has a smaller mass, it still experiences the same force as the larger object due to the gravitational field. When two magnets are fully attracted, the net force is still present but cannot cause any further motion as the magnets are in contact with each other.
  • #36
I used tiny "magnets" yet the popular term is small tiny loops :P
but I like to make it simpler to imagine it :)
 
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  • #37
Thank you all.
I'll have to study a bit more I guess...
 
  • #38
But I wonder...
In a general came of two charges you have Coulombs law to measure the force between them...
But with permanent magnets their's nothing?
Or even a magnet/electromagnet set up.

@Simon Bridge I looked at the link you shared couldn't find what I needed...
 
  • #39
Another problem about:
F = km1m2/r^2

Is that there is a distance between m1 and m2.
But as the distance decreases in case of attraction the force increases.
Same with repulsion, as the distance decreases between them the force increases.
Another problem to face.
 
  • #40
Yep - that's an approximation for long distances like the webpage says.
 
  • #41
Simon Bridge said:
You keep telling me I'm right and you've got what I am saying and then proceed to totally ignore what I've told you!

You will never have magnets which have a meaningful rating in Newtons or any other unit of force.
Your question has no meaning.

Magnet strength is rated in units of Gauss at the poles - or by some method related to the Gauss rating by a formula.

Please provide a link to a site which gives a rated force in Newtons for it's magnets.

Well you're right.
Gauss is the proper and best unit of measurement for this.
But I think, treating the force in "N" is a good way to guess as you said, to know how much force this magnet's pole is capable of applying.
Keep in mind Phztastic, that each magnet's pole has a certain amount of FORCE it can apply. Of course the two poles of magnet(1) is equally the same. Meaning(Using N to make you understand) if a North pole has an ability to "pull/push" with a force of 100N the same is said about the S pole.
Don't relie on "N" in your calculations, if you want to get a grasp of the amount of "FORCE" you have with that pole sure or even in the system, that's fine. But its not 100% accurate.

Remember, in a electromagnet-magnet interaction its not the same as two permanent magnets.
Having two magnet = the same force always being apply on each other with no change.
If you have an electromagnet it can "change" the amount of force it applies on the magnet by changing the flow of current(I), but the magnet's force stays the same.
The magnet's force ALWAYS stay's the same in a setup(If nothing effect's its field or anything else).

Example:
Electromagnet & Magnet system:
Magnet's N pole applies a force of 1N
Electromagnet's power source = 5V-12V, the S pole force = 1-15N
If you change the flow of current(I) of the electromagnet the force from that flow changes, however, the force of the magnet will always stay the same at 1N it can't increase/decrease at this system.

This is all based of my observations and experiments
Let me know if you have questions, and PLEASE correct me if I'm wrong here.
 
  • #42
Thank you all!
I think I've got what I need.
 
  • #43
It even make more sense!
When I think of an electric-motor. A motor would not work without Newton's 3rd law.
Nothing in fact would work without Newton's 3rd law!
 
  • #44
OF COURSE! Good example btw. A motor is a prefect illustration!
Newton's 3rd law is a description of a natural phenomena.
That occurs every second of our daily lives :)
 
  • #45
I used F = km1m2 / r^2
The results are not realistic!

I assumed that m1 and m2 are two poles rated in Gauss.
K = 8.99x10^9 ( I could only find this.)
And r = 0.01 (Wanted to see the results close to zero.)

The number was 8 figure+!
Use any example. Let m1 = 100G and m2
Let the distance = 0.01 and see it for yourselves.
 
  • #46
Even by converting G = Tesla would still make no sense...
 
  • #47
One top of that! There is not one example! Of calculating the force between two poles anywhere!
A example that helps that is...
 
  • #48
Unless I'm calculating it wrong?

I used simple values M1 = 100Gauss M2 = 100Gauss r =0.01M
K = 8.99x10^9

F = K M1M2/ r^2

So I substituted all the values and figured out the force was a huge number!
Are you all sure this formula is the one I should use? Or is there another one?
 
  • #49
Phztastic said:
Unless I'm calculating it wrong?

I used simple values M1 = 100Gauss M2 = 100Gauss r =0.01M
K = 8.99x10^9
If you are using the equation for the force between two electromagnets given in the reference I supplied earlier, then this value appears to be about 16 orders of magnitude too big - you need to check the units. Note also: "Gauss" is not the unit for magnetic pole strength used in that reference.

The correct values and units for use with the equation are given in the reference.

Here is that reference again:
http://en.wikipedia.org/wiki/Electromagnet#Force_between_electromagnets

For the general case, you will be interested in:
http://en.wikipedia.org/wiki/Force_between_magnets

If you do not read the references, I cannot help you.
 
  • #50
Simon Bridge said:
If you are using the equation for the force between two electromagnets given in the reference I supplied earlier, then this value appears to be about 16 orders of magnitude too big - you need to check the units. Note also: "Gauss" is not the unit for magnetic pole strength used in that reference.

The correct values and units for use with the equation are given in the reference.

Here is that reference again:
http://en.wikipedia.org/wiki/Electromagnet#Force_between_electromagnets

For the general case, you will be interested in:
http://en.wikipedia.org/wiki/Force_between_magnets

If you do not read the references, I cannot help you.

The first link is not working.
Im guessing its a link to "electromagnets" in wikipedia? I'm reading it.
 
  • #51
By Newton's 3rd Law, YES:D

magnets can apply force to a lot of things, eg. another magnet, magnetic metals, charge, etc.
and the forced are calculated in different ways.
For example:
1) Forces between two magnets: http://en.wikipedia.org/wiki/Force_between_magnets
2) Forces between a magnetic field and a charge : Lorentz force - F = qv×B
 
  • #52
Simon Bridge said:
If you are using the equation for the force between two electromagnets given in the reference I supplied earlier, then this value appears to be about 16 orders of magnitude too big - you need to check the units. Note also: "Gauss" is not the unit for magnetic pole strength used in that reference.

The correct values and units for use with the equation are given in the reference.

Here is that reference again:
http://en.wikipedia.org/wiki/Electromagnet#Force_between_electromagnets

For the general case, you will be interested in:
http://en.wikipedia.org/wiki/Force_between_magnets

If you do not read the references, I cannot help you.


I read both articles.
Ampère's model is really complicated... How can I figure out m1 and m2?
I can't find any references that give out examples. I can't learn this by my own it way to complicated...
 
  • #53
I'm not sure what a magnet "moment" even is... Could any of you elaborate?
 
  • #54
Most cases of the magnetic moment is relevant to a current carrying loop...
Nothing about magnets.
Its helpful interms of the a electromagnet, but what about a manget?
 
  • #55
The first link is not working.
Im guessing its a link to "electromagnets" in wikipedia? I'm reading it.
The first link was the one you got the original k.m1.m2/r^2 equation from. It works for me. But you are right - it links to the "electromagnets" page in wikipedia.

I read both articles.
Ampère's model is really complicated... How can I figure out m1 and m2?
... Magnetism is complicated, yes. Sorry.
You figure out the magnetic pole strengths for electromagnets by following the definition - the first link gives you an equation.
Note: did you try using the Gilbert Model?
I can't find any references that give out examples. I can't learn this by my own it way to complicated...
Trawl the college electromagnetism courses. This is not normally taught before second year.

I'm not sure what a magnet "moment" even is... Could any of you elaborate?
Did you look it up?

Most cases of the magnetic moment is relevant to a current carrying loop...
Nothing about magnets.
Its helpful in terms of the a electromagnet, but what about a magnet?
You can model any magnet with a magnetic dipole .. that's why you have "north" and "south" poles.
The Gilbert model is more useful for permanent magnets - but it can depend on what you plan to do with it.

Note: at the bottom of this page are five similar threads in PF.
Have you looked to see what other people did?
 
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  • #56
I studied a college level lecture that deal's with the relation of magnetic field and a electric field and relativity mathematically.

But when solving F of a pole. (N/S) For example: S is attracted to the N pole, I'd have to figure out the pole strength of S in Ampere*m^2 and divided it by r. So , F = (k) M1/r^2
The good news for me is, that knowing the force that magnet's pole experiences is dependent on that magnet's pole as M1. That was very informative.
F = (k) M1M2/ r^2 shows me that the total force between the two magnets is caused DUE to BOTH poles. Meaning the two poles are responsible for the force.

Ampere's model is to hard to figure out... Gilbert's model is very useful to give me a general idea but bad to relie for correct values.

I'm not sure about magnetic moments, but all I know is that it's the force a that a magnet(dipole) can exert and experience from another magnetic field(Please correct me if I'm wrong I feel that I'm off track!).

I'll try to get used to the magnetic dipole models... It tough but I'll try.
I'll most likely use F = k m1m2 / r^2, with permanent magnets interactions and electromagnets because it just gives me the idea of what's going on, and is most commonly used in examples...

Also studying Magnetic potential energy. A question though, The higher the magnetic moment the greater the field thus the greater the MPE? The energy is low when the poles are aliened the energy is high when the poles are not aliened.

I've read other threads it give a bit of detail.
Please do share you're ideas about what I've said, and if I said anything wrong... Do correct me with a brief explanation... I've been studying this for a while.
 
  • #57
If only I can figure out an easy way to know the "pole strength" of each pole that would make my life easier!
Simon could you tell me how would you figure out such a thing? What methods would you use?
Or could you site me an exact reference?

BTW, is the K = 8.99x10^9 ?
 
  • #58
you (post #57 above) said:
BTW, is the K = 8.99x10^9 ?
me (post #49) said:
you (post #48) said:
K = 8.99x10^9
If you are using the equation for the force between two electromagnets given in the reference I supplied earlier, then this value appears to be about 16 orders of magnitude too big - you need to check the units. Note also: "Gauss" is not the unit for magnetic pole strength used in that reference.
...
The correct values and units for use with the equation are given in the reference.

You have read the reference (you: post #52), but you did not see the correct value??

Are you having trouble reading or understanding the references?
Will you be better served reviewing core skills?
 
  • #59
Well I assumed it is. While reading I didn't fine it no.
Still, how can I figure out the magnitudes of each pole in Ampere*m^2?

Well, the reference give out a lot of information but, I didn't find the explanation of how to measure the pole strength for example?

I'd just want to know the answer to that question first before moving one or going back, because right now I'm stuck!
 
  • #60
But how about my understanding of the magnetic moment and magnetic potential energy.
Is it correct?
 
<h2>1. How do charges/magnets/electromagnets attract or repel each other?</h2><p>Charges/magnets/electromagnets attract or repel each other based on their electric or magnetic fields. Like charges/magnets/electromagnets repel each other, while opposite charges/magnets/electromagnets attract each other.</p><h2>2. What causes the attraction or repulsion between charges/magnets/electromagnets?</h2><p>The attraction or repulsion between charges/magnets/electromagnets is caused by the interaction of their electric or magnetic fields. These fields exert forces on each other, resulting in attraction or repulsion.</p><h2>3. How does distance affect the strength of attraction or repulsion between charges/magnets/electromagnets?</h2><p>The strength of attraction or repulsion between charges/magnets/electromagnets decreases as the distance between them increases. This is because the electric or magnetic fields weaken with distance.</p><h2>4. Can the strength of attraction or repulsion between charges/magnets/electromagnets be changed?</h2><p>Yes, the strength of attraction or repulsion between charges/magnets/electromagnets can be changed by altering the magnitude of the charges or the strength of the magnetic field. It can also be changed by changing the distance between the objects.</p><h2>5. How is the attraction or repulsion between charges/magnets/electromagnets used in everyday life?</h2><p>The attraction or repulsion between charges/magnets/electromagnets is used in many everyday devices, such as electric motors, generators, and speakers. It is also essential in technologies like MRI machines and particle accelerators.</p>

1. How do charges/magnets/electromagnets attract or repel each other?

Charges/magnets/electromagnets attract or repel each other based on their electric or magnetic fields. Like charges/magnets/electromagnets repel each other, while opposite charges/magnets/electromagnets attract each other.

2. What causes the attraction or repulsion between charges/magnets/electromagnets?

The attraction or repulsion between charges/magnets/electromagnets is caused by the interaction of their electric or magnetic fields. These fields exert forces on each other, resulting in attraction or repulsion.

3. How does distance affect the strength of attraction or repulsion between charges/magnets/electromagnets?

The strength of attraction or repulsion between charges/magnets/electromagnets decreases as the distance between them increases. This is because the electric or magnetic fields weaken with distance.

4. Can the strength of attraction or repulsion between charges/magnets/electromagnets be changed?

Yes, the strength of attraction or repulsion between charges/magnets/electromagnets can be changed by altering the magnitude of the charges or the strength of the magnetic field. It can also be changed by changing the distance between the objects.

5. How is the attraction or repulsion between charges/magnets/electromagnets used in everyday life?

The attraction or repulsion between charges/magnets/electromagnets is used in many everyday devices, such as electric motors, generators, and speakers. It is also essential in technologies like MRI machines and particle accelerators.

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