measure magnetic attraction versus distance
measure magnetic attraction versus distance
(OP)
I mave measured attraction versus distance, my results are a little unexpected and I want to compare mine with someone else's. But I do not know he did similar experiments. If someone could give me a person's name, I will be grateful.





RE: measure magnetic attraction versus distance
TTFN
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RE: measure magnetic attraction versus distance
On log-log paper that gives a line with slope 2:1. For all 6 different sets of magnets the points lie an a perfect straight line, but their slope is alike, but far from 1:2.
What I am after is confirmation that more people have measured that, and if so, how they explain it.
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By the way: When you let the distance decrease slowly, the magnets (which one?) do the work F * \delta l. Where does that energy come from? The only thing I can think of is internal energy, which means that they grow colder. Has anybody measured that? Does there exist a book on the thermodynamic theory of magnetism?
One more, probably stupid question:
Suppose I have a copper wire from me to the other end of the table, 5 cm above the table. Current from me to the other end, 15 - 20 Amperes.
I move a compass across the table under the wire. Which way can I expect the pointer marked "N" of my compass will point to? Left or Right?
To make sure that my compass 'feels' the circular field I move it to above the wire. As expected the compasneedle turns to its opposite.
It should be a simple question: What do you expect and why:
a. When below the wire, the pointer marked "N" points to my left, when above to my right
or.
b. below to my right right, when above left?
And I will be very grateful to the one who makes me understand the meaning of "Permeability" of "Nothing".
N
RE: measure magnetic attraction versus distance
Otherwise, if you go to the mechanical engineering other topics, you'll find a post on movement of overhead conductors which relates to your post.
RE: measure magnetic attraction versus distance
TTFN
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RE: measure magnetic attraction versus distance
But a nobody can build a safe, reliable house, let it be a skyscraper, on a lousy foundation. So before I can do anything I must make sure I understand the foundations in all details.
So please answer the simple questions, you will see they are not as 'silly' as you think they are.
RE: measure magnetic attraction versus distance
TTFN
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RE: measure magnetic attraction versus distance
It's not a trick question, it's not obvious to me how we would come to that conclusion.
I think you start by drawing an analogy to electrical circuit.
We have two dipoles separated by a distance R >> r where r is the characteristic distance of the dipole.
The far-field behavior for a dipole is 1/R^3 (drops off faster than the point charge 1/R^2 since the effects of the equal/opposite charges of a dipole tend to cancel each other at a distance).
How does the other dipole react to the field from the first? Its reaction can be predicted in terms of a torque based on field strength, dipole strenght, and angle relative to the field. How are we tranlating that torque to a force?
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(2B)+(2B)' ?
RE: measure magnetic attraction versus distance
https://en.wikipedia.org/wiki/Dipole#Magnitude