Plot field values along a user-specified line or...?

["Johnson" <femmuser@xxxxxxxxx>]

I'm new to the Femm. Maybe this is wrong question but I'll ask it 
anyway.

When I want to display results I click on the "glasses icon". Then I 
define contours for line integrals 
and plots. Then I click on button, 7th from a left, "Plot field values 
along a user-specified line". 

The small pop-up box appears "X-Y plot of field values". Now I have 
choice of 7 plot types, like 
"Magnitute of flux density" or "normal field intensity" etc.

Which one do I need in order to calculate electromotive force from a 
(electro)magnet to lets say, 
metal object. To be more precise, I want to calculate the strength 
that magnet will have on 
area(object). Something like in a example "of four of horseshoe-shaped 
electromagnets" - in brg.html, 
where it says 
Maximum Force 460 N 
Maximum Current 12 A 
How do you get those numbers, and what does Maximum current mean in 
this case?

Which parameter I need to pay attention at, or do I need to click on 
button "define areas over which 
integration can be performed".