magnet to magnet force?

[vlad777]

**broken link removed**



These are results of the measurement:

mm| grams
81| 1
68| 2
60| 3
58| 4
55| 5
50| 6
47| 9
40| 15
37| 21
32| 33
28| 47
25| 62
21| 110
15| 254
12| 380
10| 430
7| 1000


My main question is:

If I know B1 for a point in space and then
introduse permanent magnet of a known B2 to that point
whaqt will be the force on permanent magnet?


Many thanks.

 

[vlad777]

**broken link removed**

If you consider this then there is no way to calculate F from B without including in your equations
atomic currents or electric charge...

Edit:

What about replacing permanent magnet with electromagnet with no core that produces equivalent B?
Equivalent electromagnet, but if we don't know N or I what is the overall description?
Something that measures in C*m/s .
A*m?

Edit2:

pole strength:
https://en.wikipedia.org/wiki/Ampere-meter

 

[BrownOut]

I"ve wondered the same thing myself. I wanted to calculate the force on a relay plunger, for instance, but I could never find an equation. And that despite I studied electro magnitism in college.

 

[Mr RB]

If in doubt, measure. Something like a relay plunger will depend a lot on the exact mechanical contruction so I don't think any calc will be worth doing.

 

[vlad777]

Could the formula be:

F= B1 * H2 * S

F-force
B1-magnetic field in the point
H2-magnetic field strength of the magnet
S- surface of the magnet pole

What do you think?


Edit:
I found the answer on wikipedia:
https://en.wikipedia.org/wiki/Force_between_magnets

 

[alec_t]

For two permanent magnets of strengths H1 and H2 the force between them is proportional to H1*H2 divided by the square of their separation, IIRC.

 

[Mr RB]

Yes but he said "calculate the force on a relay plunger". Every relay I've seen had some type of iron frame on the coil, and the armature completes some magnetic path within the iron frame so you can't do a force calc based on the coil characteristics (ie; current, number or turns). You need to know all the characteristics of the mechanical construction including the iron frame and/or armature. Empirical measurement of the force is a much better option.