OneOwOne 2 years ago Are these set-ups equal? Magnet A(1) = 20g ceramic magnet Magnet B(1) = 80G ceramic magnet Setup - 1: Magnet A and another Magnet A(2 equal magnets in mass + strength)are being attracted by the force of attraction. Set - up 2: Magnet B(80G) and another Magnet A(2 NON-equal magnets in mass + strength)are being attracted by the force of attraction. Is the force of attraction applied in both cases equal? @Vincent-Lyon.Fr @Mashy The question is about comparing the total force of attraction in different set-ups.

1. Mashy

ok they are not equal .. ! cause you are comparing A-A vs A-B .. so definitely not equal!

2. OneOwOne

3. OneOwOne

You gave me a general not specific answer :P @Mashy

4. Mashy

as i told you before.. force put by A depends on WHAT it is putting force on in first case A is putting force on A second case A is putting force on B .. so obviously they ll be different :-/ why don't you get the concept of force fields??? A sets up a field.. then for some particle to experience a force in that field, it depends on the property of that particle..

5. OneOwOne

I'm really struggling with the concept!

6. OneOwOne

@Mashy What about this statement: "If you bring a heavier magnet then it means the pole strength is stronger.. and hence you see the q values in the above equations become stronger and thus the force of attraction is stronger.. " Heaver magnet is B in setup 2, this the pole strength is stronger... And the Q values are stronger thus the force of attraction= stronger? Is they BY ANY CHANCE making sense?

7. OneOwOne

You know what I'm doing? Thinking about you statement and relating it to setup#2.

8. OneOwOne

Setup#2 will have more force than setup #1. Thats because... Of B. Im trying to understand the concept of forces but I'm struggling severely.

9. OneOwOne

@gleem

10. OneOwOne

@jim_thompson5910 @Callisto @completeidiot @ghazi

11. OneOwOne

12. Mashy

yes correct.. thats correct i see light finally :D.. the pole strength of B is stronger.. and hence in set up 2 .. the force will be stronger :D..

13. Mashy

so remember both the pole strengths come into play!!.. force = product of pole strengths of the interacting magnets!

14. Mashy

not equal.. i meant proportional.. !!

15. Mashy

otherwise you ll take my word for it and smother me later :D

16. OneOwOne

@Mashy FINALLYYY!!!! ooooowhooo!

17. Mashy

yea :D.. remember this is true for ALL FORCE FIELDS!

18. OneOwOne

Thanks mate for all the help...

19. Mashy

no problem ;-)

20. OneOwOne

@Vincent-Lyon.Fr YOUR LEFT TO CONVINCE AND SEE THE LIGHT! :P

21. Mashy

he ll come and kill you :D..

22. OneOwOne

ooow noo! :\$

23. OneOwOne

I've been trying to explain what I ment for a while... But finally you can understand now so yea :P

24. rajathsbhat

I'm assuming that the magnets are as strong as they can be. There are 4 times as many atoms in B as there are in A. Think of these atoms as strong men of equal strength. If they're trying to pull a huge truck, obviously Team B has a better chance of getting it moving because they pull with 4 times as much force as Team A. And because the two magnets don't move, Magnet A exerts as much force on Magnet B as B does on A (i.e. four times as much as that in setup 1). This follows directly from Newton's Third law.

25. OneOwOne

Ow forgot to note, magnet B is fixed, while magnet A is free moving.

26. OneOwOne

@rajathsbhat And that means set up 2 will have almost 2.5 times greater force than set up 1 40G vs 100G = 100G greater force than the first set up. And yes, newton's third law is applied equally.

27. OneOwOne

So @Vincent-Lyon.Fr I am I making sense here?

28. gleem

I posted this recently on your last edition of this issue. Lets begin again. One thing that was left uncorrected in the previous discussion is that the pole strength is related to the mass of the magnet it is not... A light magnet can be much stronger than a heavy one. A term which should be eliminated from this discussion is "rate of force" It means nothing to me and I am sure to many others. OK? You say you have done some experiments with magnet but from reading above you did not use instruments to measure forces but used the feel of the force to gauge its strength which is very subjective. A light strong magnet is indistinguishable from a heavy weak magnet. in fact you cannot determine which one is stronger from their interaction. You can determine which one is stronger using a third magnet to interact with each separately. Do you see that? To demonstrate the force between the two magnets is the same strength consider the diagram with two different strength and size magnets separated by a rigid non magnetic wall with two identical springs between the wall and each magnet. |dw:1360951375404:dw| . You would find that the compressed length of each spring is the same demonstrating the force on each magnet is the same. The force on A due to B is equal to the force on B due to A. I'll stop here and see what you think.

29. rajathsbhat

Yes, I was wrong in thinking that the force exerted by each magnet depends only on that magnet alone. After a little reading and thinking, I realized that the force exerted by/on each magnet depends on the strength of the field of the both the magnets but it's not like it's a simple combination of the two fields. In other words, your comparison of the forces based on the total masses of the two systems in not correct (I think). Because it depends (a lot) on the dimensions of the magnets. |dw:1360955110744:dw| You see, the force on little magnet depends on a) the force with which c attracts b b) the force with which d repels b c) the force with which c repels a d) the force with which d attracts a. So it's not just about the attractions. That said, I couldn't find an equation for the force exerted by/on each of these magnets in such a system. Lemme know if you want some clarification.

30. gleem

The magnetic pole concept is a carry over from the electric charge concept magnetic poles i.e., have not be found although there are reasons why they might exist. However we always find them in " pairs" as as such the create what we call a dipole. analogous to its electrical counterpart. Unlike charges they are just constructs created to help us model the magnetic field and the effects of magnets and currents on magnets. Because they are dipoles when placed in a magnetic field they experience a torque and twist to align themselves with the field and because the two closest pole have a stronger influence their force predominates . The magnetic force is of the same form as the coulomb force ie m1m2/R^2 where m1 and m2 are the strength of the poles measured in amp*m^2. It is correct to consider n-s, s-n, s-s and n-n interactions when two magnets get close to feel one another fields. And you see although the fields are not necessarily dependent on size how they respond does depend of size and mass. Longer magnets will twist slower than short magnets. and heavy magnets respond slower than light magnets. Is this making sense?

31. OneOwOne

@gleem @rajathsbhat I do understand that the attraction force is not as simple as I preserved it to be. However, the example is based on TWO magnets of equal type, similar field strengths. I've conducted another experiment using two Neo magnets one 4200Gauss and the other is 4250 Gauss, the weaker field represents the smaller magnet. Indeed, the force is dependent on many many factors. But... @gleem My point still stands in your case. Due to that small light magnet a strong force of attraction/repulsion can be applied. @gleem your making perfect sense, but I'd doubt my experiment was subjective... Compare between two equal magnets and two disimilar ones. You'd feel a higher force in one of the cases.

32. OneOwOne

@gleem if you do not with my previous statement. Explain to me why is it that when I did my experiment I found that a stronger force was felt in the second setup than the first? You can measure a difference in force by just feeling the set up.

33. OneOwOne

@rajathsbhat What do you think?

34. OneOwOne

I do agree with the facts your giving but... When I try to just feel the forces I find another result. I think the spring test would be the same equal thing @gleem + They could possibly compress the spring instantly that you might think they are equal but I doubt they are. That would mean all Neodymium magnets from the range 4100 - 4300 of different masses are equal. < Thats wrong.

35. OneOwOne

4100-4300 Gauss.

36. rajathsbhat

If all you're trying to do is get a qualitative feel for the forces, you're right - you'll feel a much stronger pull incase of setup B. And you should be able to justify this from my reasoning so far.

37. OneOwOne

Yea, I can feel a much stronger pull, and in fact there is a much stronger pull. @rajathsbhat

38. OneOwOne

However, other factors on how his is possibile I don't know. But! I can say that in ANY case this will always happen.

39. OneOwOne

But I can say that the force of attraction is certainly dependent on BOTH magnets. If one is higher in strength it will increase the total force of attraction. @gleem I agree with you that mass in not the main factor and rate of force makes no sense. But bring two neo. magnets of similar magnetic fields but different masses and you'll see the difference.

40. OneOwOne

@rajathsbhat how can I use your point to support my claim?

41. OneOwOne

@gleem I doubt I need a third magnet Its going to mess up a few things :P

42. rajathsbhat

here's a nice analogy: do you know how tough (sometimes impossible) it is to separate two books whose alternate pages overlap?

43. OneOwOne

yes.

44. rajathsbhat

so think of it like this: setup A = the two books are a 100 pages each setup B = the two books are phone books (1000+ pages) The papers are analogous to the fields. It's much harder to separate the second setup than it is to separate the first one.

45. OneOwOne

So... @rajathsbhat this is your support. It makes sense when the two magnets are stuck to each other.

46. OneOwOne

Set up B will be more difficult to separate. Which would also support the idea that there is more strengt here than the first set up.

47. rajathsbhat

yup. This analogy also works when you're holding them apart, separated only by a small distance.

48. gleem

Again size ie mass makes no difference in the force. As a physicist you should use instruments to measure the force. get fish scales (for weighing fish) and connect one to each magnet and take a reading. If the forces are different the readings will be different.

49. OneOwOne

@gleem The point is not the size. Its the strength difference between both set ups. And the reason WHY there is the difference is due to the mass. Conducting the experiments you've pointed out would make no huge difference. They still will show that the force of setup 2 is greater, because feeling a force is quite enough :) As a practicing physicist... I should find most convenient ways to test things and this was. Finally I'd ask you @gleem Why is it in step up 1 I feel a weaker force pushing against my fingers in comparison to set up 2? Set up 2 has a more stronger force pushing against my fingers. Thats obviously shows a difference. And I've conducted this test multiple times with multiple people.

50. gleem

Mass is irrelevant only strength is important. the only reason a more massive magnet is stronger is that the magnetic moment per unit volume is higher. In a real experiment to determine the effect of a property on the behavior of a system is to hold all properties fixed except the one of interest and vary that one to see how the system behaves. You can do this using solenoids with a non magnetic core of different masses. By adjusting the current and or the windings you fix the field strength. Vary the mass of the core and determine the force.

51. OneOwOne

@gleem so you do agree in set up 2 there is more strength/force/magnetic moment etc... than set up 1? The experiment you've hinted will be tested soon. Till then I used the basic feel for a human sense to determine the difference.

52. gleem

I think 2 has a greater force than one only because the pole strength is larger not because the magnet is more massive. If a and b are made out of the same material then magnetic pole strength correlates with mass since each magnet being of the same material has the same magnetic moment per unit volume. ergo the bigger magnet has the greater pole strength.

53. OneOwOne

@gleem Thanks. Pretty much summed up my point! Thank you all!