
#1
Dec1007, 11:29 PM

P: 7

1. The problem statement, all variables and given/known data
Use Ampere’s law to calculate the magnetic field inside of a toroid with 850 turns. The inner radius of the rectangular coils is 3.00 cm, the outer radius is 7.00 cm. 2. Relevant equations ampere's law: path integral(B*ds) over a closed path is equal to the enclosed current times mu_0 3. The attempt at a solution by ampere's law for toroids, I get B= mu_0*N*I/(2*pi*R) Im confused as to what the inner and outer radius have to do with this problem, hence the cry for help :( anyone ? 



#2
Dec1107, 06:56 AM

Emeritus
Sci Advisor
PF Gold
P: 4,975

The two radii are there so you can determine the axis of toroidal coils. This is chosen as it simplifies Amperes circuital law to the equation you have stated.




#3
Dec1107, 05:39 PM

P: 7

so basically these numbers dont really matter, right ?
since Im finding the magnetic field inside the toroid, its just gonna be r as an arbitrary length from the center to some point inside (between 3 and 7 cms) ....correct ? if so, then the final solution is mu_0*850*I/(2*pi*R), right ? 



#4
Dec1107, 06:43 PM

Emeritus
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PF Gold
P: 4,975

Magnetic Field in a Toroid
If you have a look at the following page it may become clearer.
http://hyperphysics.phyastr.gsu.edu...ic/toroid.html 



#5
Dec1107, 07:37 PM

P: 7

so from that explanation, I got that since inner radius is 3 and outer is 7, then radius of the rectangular crosssection is 4/2=2
so r=3+2=5 thats about as much as I could get from that page, please let me know If Im still missing something... 



#6
Dec1107, 08:00 PM

Emeritus
Sci Advisor
PF Gold
P: 4,975

That should be ok.



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